Endangered and Threatened Wildlife and Plants; Removing the Kirtland's Warbler From the Federal List of Endangered and Threatened Wildlife

Federal Register, Volume 84 Issue 196 (Wednesday, October 9, 2019)
[Federal Register Volume 84, Number 196 (Wednesday, October 9, 2019)]
[Rules and Regulations]
[Pages 54436-54463]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-22096]
[[Page 54435]]
Vol. 84
No. 196
October 9, 2019
Part V
Department of the Interior
Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Removing the Kirtland's
Warbler From the Federal List of Endangered and Threatened Wildlife;
Final Rule
Federal Register / Vol. 84 , No. 196 / Wednesday, October 9, 2019 /
Rules and Regulations
[[Page 54436]]
Fish and Wildlife Service
50 CFR 17
[Docket No. FWS-R3-ES-2018-0005; FXES11130900000]
RIN 1018-BC01
Endangered and Threatened Wildlife and Plants; Removing the
Kirtland's Warbler From the Federal List of Endangered and Threatened
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Final rule.
SUMMARY: Under the authority of the Endangered Species Act of 1973, as
amended (ESA), we, the U.S. Fish and Wildlife Service (Service), are
removing the Kirtland's warbler (Setophaga kirtlandii) from the Federal
List of Endangered and Threatened Wildlife (List) due to recovery. This
determination is based on a thorough review of the best available
scientific and commercial information, which indicates that the threats
to the species have been eliminated or reduced to the point that the
species has recovered and no longer meets the definition of endangered
or threatened under the ESA. This rule also announces availability of a
post-delisting monitoring plan for Kirtland's warbler.
DATES: This rule is effective November 8, 2019.
ADDRESSES: This final rule and the post-delisting monitoring plan are
available on the internet at http://www.regulations.gov under Docket
No. FWS-R3-ES-2018-0005 or https://ecos.fws.gov. Comments and materials
we received, as well as supporting documentation we used in preparing
this rule, are available for public inspection at http://www.regulations.gov. Comments, materials, and documentation that we
considered in this rulemaking will be available by appointment, during
normal business hours at: U.S. Fish and Wildlife Service, Michigan
Ecological Services Field Office, 2651 Coolidge Road, Suite 101, East
Lansing, MI 48823; telephone 517-351-2555.
Michigan Ecological Services Field Office, 2651 Coolidge Road, Suite
101, East Lansing, MI 48823; telephone 517-351-2555. If you use a
telecommunications device for the deaf (TDD), please call the Federal
Relay Service at 800-877-8339.
Executive Summary
    Why we need to publish a rule. Under the Endangered Species Act, a
species may be removed from the List (``delisted'') if it is determined
that it has recovered and is no longer endangered or threatened.
Delisting can be completed only by issuing a rule.
    This rule removes the Kirtland's warbler (Setophaga kirtlandii)
from the List.
    Basis for action. Under the ESA, we determine that a species is an
endangered or threatened species based on any of five factors: (A) The
present or threatened destruction, modification, or curtailment of its
habitat or range; (B) overutilization for commercial, recreational,
scientific, or educational purposes; (C) disease or predation; (D) the
inadequacy of existing regulatory mechanisms; or (E) other natural or
manmade factors affecting its continued existence. We must consider the
same factors in delisting a species. We have determined that the
primary threats to the Kirtland's warbler have been reduced or managed
to the point that the species is recovered.
    Peer review and public comment. We sought comments on the proposed
delisting rule and draft post-delisting monitoring plan from
independent specialists to ensure that this rule is based on
scientifically sound data, assumptions, and analyses. We also
considered all comments and information we received during the proposed
delisting rule's comment period.
Previous Federal Actions
    On April 12, 2018, we published a proposed rule to remove
Kirtland's warbler from the List (83 FR 15758). Please refer to that
proposed rule for a detailed description of previous Federal actions
concerning this species.
Species Information
    The Kirtland's warbler is a songbird classified in the Order
Passeriformes, Family Parulidae. This species was originally described
in 1852, and named Sylvicola kirtlandii (Baird 1872, p. 207). The
American Ornithologists' Union Committee on Classification and
Nomenclature-North and Middle America recently changed the
classification of the Parulidae, which resulted in three genera
(Parula, Dendroica, and Wilsonia) being deleted and transferred to the
genus Setophaga (Chesser et al. 2011, p. 606). This revision was
adopted by the Service on February 12, 2014 (78 FR 68370; November 14,
    The Kirtland's warbler is a neotropical migrant that breeds in jack
pine (Pinus banksiana) forests in northern Michigan, Wisconsin, and
Ontario. This species has one of the most geographically restricted
breeding distributions of any mainland bird in the continental United
States. Breeding habitat within the jack pine forest is both highly
specific and disturbance-dependent, and likely was always limited in
extent (Mayfield 1960, pp. 9-10; Mayfield 1975, p. 39). Similarly, the
known wintering range is primarily restricted to The Bahamas (Cooper et
al. 2019, p. 83).
    Kirtland's warblers are not evenly distributed across their
breeding range. Female Kirtland's warblers are often observed with
singing males; therefore, nesting is generally assumed to occur at most
sites where singing males are present (Probst et al. 2003, p. 369;
MDNR, USFWS, USFS, unpubl. data). More than 98 percent of all singing
males have been counted in the northern Lower Peninsula of Michigan
since population monitoring began in 1951 (Michigan Department of
Natural Resources (MDNR), Service (USFWS), U.S. Forest Service (USFS),
unpubl. data). The core of the Kirtland's warbler's breeding range is
concentrated in five counties in northern lower Michigan (Ogemaw,
Crawford, Oscoda, Alcona, and Iosco), where nearly 85 percent of the
singing males were recorded between 2000 and 2015, with over 30 percent
counted in Ogemaw County alone and over 21 percent in just one township
during that same time period (MDNR, USFWS, USFS, unpubl. data).
    Kirtland's warblers have been observed in Ontario periodically
since 1900 (Samuel 1900, pp. 391-392) and in Wisconsin since the 1940s
(Hoffman 1989, p. 29). Systematic searches for the presence of
Kirtland's warblers in States and provinces adjacent to Michigan,
however, did not begin until 1977 (Aird 1989, p. 32; Hoffman 1989, p.
1) and have not been conducted consistently across the years. Shortly
after these searches began, male Kirtland's warblers were found during
the breeding season in Ontario in 1977 and Quebec in 1978 (Aird 1989,
pp. 32-35), Wisconsin in 1978 (Tilghman 1979, p. 19), and the Upper
Peninsula of Michigan in 1982 (Probst 1985, p. 11). Nesting was
confirmed in the Upper Peninsula in 1996 (Weinrich 1996, p. 2; Weise
and Weinrich 1997, p. 2), and in Wisconsin and Ontario in 2007 (Richard
2008, pp. 8-10; Trick et al. 2008, pp. 97-98). Singing males have been
observed in the
[[Page 54437]]
Upper Peninsula annually since 1993, with the majority of observations
in the central and eastern Upper Peninsula (MDNR, USFWS, USFS, unpubl.
data). In Wisconsin, nesting has been confirmed in Adams County every
year since 2007 and has expanded into Marinette and Bayfield Counties
(USFWS 2017, pp. 2-4). Scattered observations of mostly solitary birds
have also occurred in recent years at several other sites in Douglas,
Vilas, Washburn, and Jackson Counties in Wisconsin. Similarly, in
Ontario, nesting was confirmed in Renfrew County from 2007 to 2016
(Richard 2013, p. 152; Tuininga 2017, pers. comm.), and reports of
Kirtland's warblers present during the breeding season have occurred in
recent years in both northern and southern Ontario (Tuininga 2017,
pers. comm.).
    The current distribution of breeding Kirtland's warblers
encompasses the known historical breeding range of the species based on
records of singing males observed in Michigan's northern Lower
Peninsula, Wisconsin, and Ontario (Walkinshaw 1983, p. 23). In
Michigan's northern Lower Peninsula, the Kirtland's warbler's breeding
habitat is spread over an approximately 15,540-square-kilometer (km)
(6,000-square-mile) non-contiguous area. In 2015, the number of singing
males confirmed in Wisconsin (19), Ontario (20), and the Upper
Peninsula (37) represented approximately 3 percent of the total singing
male population (Environment Canada, MDNR, USFS, USFWS, Wisconsin
Department of Natural Resources (WDNR), unpubl. data), demonstrating
the species' reliance on their core breeding range in Michigan's
northern Lower Peninsula. The number of Kirtland's warblers that could
ultimately exist outside of the core breeding range is unknown;
however, these peripheral individuals do contribute to a wider
    On the wintering grounds, Kirtland's warblers are more difficult to
detect and are infrequently observed. Kirtland's warblers are unevenly
distributed across the landscape; they tend to hide in low-lying, dense
vegetation, and males do not generally sing during the winter (Currie
et al. 2003, pp. 1-2; Currie et al. 2005a, p. 97). Kirtland's warblers
winter largely within The Bahamas (Mayfield 1996, pp. 36-38; Lee et al.
1997, p. 21; Stone 1986, p. 2). The Bahamas is an archipelago of
approximately 700 low-lying islands stretching more than 1,046 km (650
miles) from near the eastern coast of Florida to the southeastern tip
of Cuba. The central islands, particularly Eleuthera and Cat Islands,
support the largest known population of wintering Kirtland's warblers
(Sykes and Clench 1998, pp. 249-250; Cooper et al. 2019, p. 85).
Wintering Kirtland's warbler have also been observed in The Bahamas on
The Abacos, Andros, Cat Island, Crooked Island, Eleuthera, The Exumas,
Grand Bahama Island, Long Island, and San Salvador (Blanchard 1965, pp.
41-42; Cooper, unpubl. data; Cooper et al. 2019, p. 85; Ewert and
Wunderle, unpubl. data; Haney et al. 1998, p. 202; Hundley 1967, pp.
425-426; Jones et al. 2013, pp. 638-641; Mayfield 1972, pp. 347-348;
Mayfield 1996, pp. 37-38; Sykes and Clench 1998, p. 250).
    Although the central islands of The Bahamas support the greatest
number of overwintering Kirtland's warblers, less frequent sightings
have been reported elsewhere in the Caribbean, including sightings from
northern Dominican Republic, coastal Mexico (Haney et al. 1998, p.
205), Bermuda (Amos 2005, p. 3), Cuba (Isada 2006, p. 462; Sorenson and
Wunderle 2017), Florida (Cooper et al. 2019, p. 85), and Jamaica
(Weidensaul 2019). These sightings may represent vagrants and do not
necessarily represent an extension of the overwintering range.
    Recent data from winter playback surveys, citizen scientists, and
light-level geolocators also indicate that the majority of
overwintering Kirtland's warblers are found in the central Bahamas,
with fewer birds overwintering in the western and eastern Bahamas and
Cuba (Cooper et al. 2017, pp. 209-211; Cooper et al. 2019, pp. 84-85).
    Although the central islands of The Bahamas support the greatest
number of overwintering Kirtland's warblers, less frequent sightings
have been reported elsewhere in the Caribbean. Of 107 accessible
reports, only 3 originated from outside of The Bahamas: Two sightings
from northern Dominican Republic, and one sighting from coastal Mexico
(Haney et al. 1998, p. 205). In addition, recent winter reports of
solitary individuals have originated from Bermuda (Amos 2005, p. 3),
Cuba (Isada 2006, p. 462; Sorenson and Wunderle 2017), Florida (Cooper
et al. 2019, p. 85), and Jamaica (Weidensaul 2019), possibly
representing vagrants and not necessarily representative of an
extension of the overwintering range.
    Although the known wintering range appears restricted primarily to
The Bahamas, many of the islands in the Caribbean basin are uninhabited
by people, may be overgrown and difficult to access, or have had
limited avian survey efforts, which may constrain our ability to
comprehensively describe the species' wintering distribution.
Kirtland's warblers readily shift sites on the wintering grounds based
on habitat availability and food resources, and they colonize new areas
following disturbance (Wunderle et al. 2007, p. 123; Wunderle et al.
2010, p. 134; Wunderle et al. 2014, p. 44). Suitable habitat may exist
on other islands, both within The Bahamas and elsewhere in the
Caribbean basin, potentially providing habitat and buffering against
the effects of catastrophic events such as hurricanes. However, the
full extent and availability of suitable habitat on the wintering
grounds has not been measured outside of the more-studied island of
Eleuthera (Wunderle 2018, pers. comm.).
Breeding Habitat
    The Kirtland's warbler's breeding habitat consists of jack pine-
dominated forests with sandy soil and dense ground cover (Walkinshaw
1983, p. 36), most commonly found in northern lower Michigan, with
scattered locations in the Upper Peninsula of Michigan, Wisconsin, and
Ontario. Jack pine-dominated forests of the northern Great Lakes region
historically experienced large, frequent, and catastrophic stand-
replacing fires (Cleland et al. 2004, p. 313). These fires occurred
approximately every 60 years, burned approximately 85,420 hectares (ha)
(211,077 acres (ac)) per year, and resulted in jack pine comprising 53
percent of the total land cover (Cleland et al. 2004, pp. 315-317).
Modern wildfire suppression has since increased the average fire return
interval within this same landscape to approximately 775 years,
decreased the amount of area burned to approximately 6,296 ha (15,558
ac) per year, and reduced the contribution of jack pine to 37 percent
of the current land cover (Cleland et al. 2004, p. 316). The overall
effect has been a reduction in the extent of dense jack pine forest,
and in turn, the Kirtland's warbler's breeding habitat.
    Kirtland's warblers generally occupy jack pine stands that are 5 to
23 years old and at least 12 ha (30 ac) in size (Donner et al. 2008, p.
470). The most obvious difference between occupied and unoccupied
stands is the percent canopy cover (Probst 1988, p. 28). Stands with
less than 20 percent canopy cover are rarely used for nesting (Probst
1988, p. 28). Tree canopy cover reflects overall stand structure,
combining individual structural components such as tree stocking,
spacing, and height factors (Probst 1988, p. 28). Tree canopy cover,
therefore, may be an important environmental cue for Kirtland's
warblers when selecting nesting areas.
[[Page 54438]]
    Occupied stands usually occur on dry, excessively drained,
nutrient-poor glacial outwash sands (Kashian et al. 2003, pp. 151-153).
Stands are structurally homogeneous with trees ranging 1.7 to 5.0
meters (m) (5.5 to 16.4 feet (ft)) in height and are generally of three
types: Wildfire-regenerated, planted, and unburned-unplanted (Probst
and Weinrich 1993, p. 258). Wildfire-regenerated stands occur naturally
following a stand-replacing fire from serotinous seeding (seed cones
remain closed on the tree with seed dissemination in response to an
environmental trigger, such as fire). Planted stands are stocked with
jack pine saplings after a clear cut. Unburned-unplanted stands
originate from clearcuts that regenerate from non-serotinous, natural
seeding, and thus do not require fire to release seeds.
    Optimal habitat is characterized as large stands (more than 32 ha
(80 ac)) composed of 8- to 20-year-old jack pines that regenerated
after wildfires, with 27 to 60 percent canopy cover, and more than
5,000 stems per hectare (2,023 stems per acre) (Probst and Weinrich
1993, pp. 262-263). The poor quality and well-drained soils reduce the
risk of nest flooding and maintain low shrubs that provide important
cover for nesting and brood-rearing. Yet as jack pine saplings grow in
height, percent canopy cover increases, causing self-pruning of the
lower branches and changes in light regime, which diminishes cover of
small herbaceous understory plants (Probst 1988, p. 29; Probst and
Weinrich 1993, p. 263; Probst and Donnerwright 2003, p. 331).
Kirtland's warblers select nest sites with higher jack pine densities,
higher percent cover of blueberry, and lower percent cover of woody
debris than would be expected if nests were placed at random (Bocetti
1994, p. 122). Due to edge effects associated with low area-to-
perimeter ratios, predation rates may be higher for Kirtland's warblers
nesting in small patches bordered by mature trees than in large patches
(Probst 1988, p. 32; Robinson et al. 1995, pp. 1988-1989; Helzer and
Jelinski 1999, p. 1449). Foraging requirements may also be negatively
influenced as jack pines mature (Fussman 1997, pp. 7-8).
    Conversely, marginal habitat is characterized as jack pine stands
with at least 20 to 25 percent tree canopy cover and a minimum density
of 2,000 stems per hectare (809 stems per acre, Probst and Weinrich
1993, pp. 261-265; Nelson and Buech 1996, pp. 93-95), and is often
associated with unburned-unplanted areas (Donner et al. 2010, p. 2).
The main disadvantage of marginal habitat is reduced pairing success
(Probst and Haynes 1987, p. 237); however, Kirtland's warblers
successfully reproduce in areas with smaller percentages of jack pine
and with significant components of red pine (Pinus resinosa) and pin
oak (Quercus palustris) in Wisconsin and Canada (Mayfield 1953, pp. 19-
20; Orr 1975, pp. 59-60; USFWS 1985, p. 7; Fussman 1997, p. 5; Anich et
al. 2011, p. 201; Richard 2013, p. 155; Richard 2014, p. 307). Use of
these areas in Michigan is rare and occurs for only short durations
(Huber et al. 2001, p. 10). In Wisconsin, however, breeding has
occurred primarily in red pine plantations that have experienced
extensive red pine mortality and substantial natural jack pine
regeneration (Anich et al. 2011, p. 204). Preliminary investigation
(Anich et al. 2011, p. 204) suggests that, in this case, a matrix of
openings and thickets has produced conditions suitable for Kirtland's
warblers, and that the red pine component may actually prolong the use
of these sites due to a longer persistence of low live branches on red
pines. Habitat conditions in documented Kirtland's warbler breeding
areas in Ontario had ground cover similar to breeding sites in Michigan
and Wisconsin, although tree species composition was more similar to
Wisconsin sites than Michigan sites (Richard 2014, p. 306). The tree
species composition at the Canadian sites also had high levels of red
pine (up to 71 percent), similar to the plantations in Wisconsin (Anich
et al. 2011, p. 201; Richard 2014, p. 307).
    Habitat management to benefit Kirtland's warblers began as early as
1957 on State forest land and 1962 on Federal forest land (Mayfield
1963, pp. 217-219; Radtke and Byelich 1963, p. 209). Efforts increased
in 1981, with the establishment of an expanded habitat management
program to supplement wildfire-regenerated habitat and ensure the
availability of relatively large patches of early successional jack
pine forest for nesting (Kepler et al. 1996, p. 16). In the late 1980s,
maturation of habitat generated through wildfire contributed to a
higher percentage of the total suitable habitat available to the
Kirtland's warbler compared to other types of habitat (Donner et al.
2008, p. 472). By 1992, artificially regenerated plantation habitat was
nearly twice as abundant as wildfire habitat, and increased to triple
that of wildfire habitat by 2002 (Donner et al. 2008, p. 472). From
1979 to 1994, the majority of singing males were found in wildfire-
generated habitat (Donner et al. 2008, p. 474). By 1994, responding to
a shift in available nesting habitat types, males redistributed out of
habitat generated by wildfire and unburned-unplanted habitat and into
plantation (planted) habitat. From 1995 to 2004, males continued
redistributing into plantations from wildfire habitat, and 85 percent
of males were found in plantation habitat by 2004 (Donner et al. 2008,
p. 475). This redistribution of males into plantations also resulted in
males being more evenly distributed across the core breeding range than
in previous years. Since 2004, the majority of Kirtland's warblers
continue to nest in plantations (USFWS, unpubl. data).
    The amount of available suitable habitat has also increased
significantly in the past 40 years due to these increased efforts by
land management agencies. The goal for 51,638 ha (127,600 ac) of
available habitat to support a recovered Kirtland's warbler population
was initially set out in the 1981 Management Plan for Kirtland's
Warbler Habitat (USFS and MDNR 1981, p. 18). Of this total,
approximately 29,987 ha (74,100 ac) of Michigan State forest lands and
about 21,650 ha (53,500 ac) of Federal forest lands were identified as
lands suitable and manageable for Kirtland's warbler breeding habitat.
That plan also provided prescriptions and guidelines to be used in
protecting and improving identified nesting habitat. Contiguous stands
or stands in close proximity were grouped into 23 areas referred to as
Kirtland's Warbler Management Areas (KWMAs). KWMAs are administrative
boundaries that describe parcels of land dedicated to and managed for
Kirtland's warbler breeding habitat. The KWMAs were further subdivided
into cutting blocks containing 200 or more acres of contiguous stands.
These acreages were determined by factoring an average population
density of one breeding pair per 12 ha (30 ac) into a 45- to 50-year
commercial harvest rotation, with the goals of producing suitable
habitat as well as marketable timber (USFWS 1985, p. 21). Data
collected from the annual singing male census from 1980 to 1995
indicated that a breeding pair used closer to 15 ha (38 ac) within
suitably aged habitat (Bocetti et al. 2001, p. 1). Based on these data,
in 2002, the Kirtland's Warbler Recovery Team (Recovery Team)
recommended increasing the total amount of managed habitat to 76,890 ha
(190,000 ac) (Ennis 2002, p. 2). Habitat management is currently
conducted on approximately 88,788 ha (219,400 ac) of jack pine forest
within MDNR (36,705 ha (90,700 ac)), USFS (49,372 ha; 122,000 ac), and
Service lands (2,711 ha (6,700 ac)) throughout the northern Lower
[[Page 54439]]
Peninsula and Upper Peninsula of Michigan (MDNR et al. 2015, pp. 22-
23), exceeding both the original and revised acreage goals.
Wintering Habitat
    On the wintering grounds, Kirtland's warblers occur in early
successional scrublands, characterized by dense, low, broadleaf shrubs
of varied foliage layers with small openings, resulting from natural or
anthropogenic disturbances (locally known as low coppice) (Maynard
1896, pp. 594-595; Challinor 1962, p. 290; Mayfield 1972, p. 267;
Radabaugh 1974, p. 380; Mayfield 1992, p. 3; Mayfield 1996, pp. 38-39;
Lee et al. 1997, p. 23; Haney et al. 1998, p. 207; Sykes and Clench
1998, p. 256; Wunderle et al. 2007, p. 123; Wunderle et al. 2010, p.
133). Kirtland's warblers predominantly overwinter in broadleaf scrub
habitat, rather than pine-dominated habitats (Cooper et al. 2019, p.
83). Suitable wintering habitat requires availability of a food source,
often fruit plants such as Erithalis fruticosa and Lantana involucrata
(see ``Diet and Foraging,'' below, for additional discussion) that are
in fruit at the right time of year, as well as availability of water.
    Historically, Kirtland's warbler winter habitat was likely created
when storm surges or other natural disturbances, such as wildfire,
removed vegetation and leaf litter (Wunderle and Ewert 2018, p. 1;
Wunderle 2018, pers. comm.), allowing for establishment of the
preferred fruit plants (which are shade-intolerant) (Fleming et al.
2015, p. 588). Human-caused disturbances may also produce suitable
habitat for Kirtland's warblers. Although goats consume the preferred
fruit plants, the plants readily regrow in open sunlight and persist,
indicating goat grazing could be an effective means of setting back
succession and creating or maintaining Kirtland's warbler habitat
(Fleming et al. 2016, p. 287). Abandonment of garden plots or other
cultivated lands are not likely to result in suitable Kirtland's
warbler habitat, because the important fruit plants are shaded out by
other, faster-growing plants (Wunderle et al., unpubl. data).
    Kirtland's warblers typically occupy wintering sites 3 to 28 years
(the mean is approximately 14 years) after human disturbance (Wunderle
et al. 2010, p. 127). As local food resources diminish in abundance,
these sites may not be sufficient to sustain an individual for an
entire winter; therefore, individuals must move widely from patch to
patch, tracking changes in fruit abundance (Wunderle et al. 2007, p.
123; Wunderle et al. 2010, p. 134; Wunderle et al. 2014, p. 44).
Migration and Stopover Habitat
    Spring departure from the wintering grounds is estimated to occur
from late April to early May, and arrival on the breeding grounds
occurs approximately 15 days later (Cooper et al. 2017, p. 212;
Rockwell et al. 2012, p. 746; Ewert et al. 2012, p. 11). Male
Kirtland's warblers have been observed arriving on the breeding grounds
between May 1 and June 5 (Petrucha 2011, p. 17; Rockwell et al. 2012,
p. 747), with the first females arriving a week or so after the first
males (Mayfield 1960, pp. 41-42; Rockwell 2013, pp. 48-49).
    Fall migration of adult males begins in late September through late
October and ends with arrival on the wintering grounds in mid-October
to early November (Cooper et al. 2017, p. 212). The earliest recorded
sighting in The Bahamas was August 20 (Robertson 1971, p. 48). Data
from recovered geolocators showed that most Kirtland's warblers
exhibited a loop migration, with fall migration occurring farther east
than spring migration (Cooper et al. 2017, p. 214). Nearly all males
departed the breeding grounds and flew in an easterly direction,
spending time in southeastern Ontario or in the eastern Great Lakes
region of the United States (Cooper et al. 2017, pp. 211, 213). Fall
migration proceeded in a general southern direction, departing the
mainland United States along the Carolina coastline (Cooper et al.
2017, pp. 211, 213). Spring migration followed a more westerly path,
with landfall occurring in Florida and Georgia (Cooper et al. 2017, pp.
213, 216). An additional stopover site was identified in the western
Lake Erie basin (Cooper et al. 2017, p. 216). An analysis of 562
records of Kirtland's warblers observed during migration found that
migration records were spread over most of the United States east of
the Mississippi River, clustered around the Great Lakes and Atlantic
Ocean coastlines (Petrucha et al. 2013, p. 383).
    Migrating Kirtland's warblers have been observed in a variety of
habitats, including shrub/scrub, residential, park, orchard, woodland,
and open habitats (Petrucha et al. 2013, p. 390). There is some
evidence that dense vegetation less than 1.5 m (4.9 ft) in height may
be important to migrating Kirtland's warblers (Stevenson and Anderson
1994, p. 566). The majority of migration records (82 percent) described
the habitat as shrub/scrub, similar in structure to what the species
uses on the breeding and wintering grounds (Petrucha et al. 2013, p.
Diet and Foraging
    On the breeding grounds, Kirtland's warblers are primarily
insectivorous and forage by gleaning (plucking insects from) pine
needles, leaves, and ground cover, occasionally making short sallies,
hover-gleaning at terminal needle clusters, and gathering flying
insects on the wing. Kirtland's warblers forage on a wide variety of
prey items, including various types of larvae, moths, flies, beetles,
grasshoppers, ants, aphids, spittlebugs, and blueberries (Mayfield
1960, pp. 18-19; Fussman 1997, p. 33). Similar taxa have been
identified from fecal samples from Kirtland's warblers, although
homopterans (primarily spittlebugs), hymenopterans (primarily ants),
and blueberries were proportionally greater in number than other taxa
among samples collected from July to September (Deloria-Sheffield et
al. 2001, p. 385). These differences in the relative importance of food
items between spring foraging observations and late summer fecal
samples may be temporal and may reflect a varied diet that shifts as
food items become more or less available during the breeding season
(Deloria-Sheffield et al. 2001, p. 386). Within nesting areas,
arthropod numbers peak at the same time that most first broods reach
the fledging stage (Fussman 1997, p. 27). Planted and wildfire-
regenerated habitats were extremely similar in terms of arthropod
diversity, abundance, and distribution, suggesting that current habitat
management techniques are effective in simulating the effects that
wildfire has on food resources for Kirtland's warblers (Fussman 1997,
p. 63).
    On the wintering grounds, Kirtland's warblers rely on a mixed diet
of fruit and arthropods. During foraging observations, 69 percent of
Kirtland's warblers consumed fruits, such as snowberry (Chiococca
alba), wild sage (Lantana involucrata), and black torch (Erithalis
fruticosa), with wild sage being the overwhelmingly predominant food
choice (Wunderle et al. 2010, pp. 129-130). Despite variation in food
availability among sites and winters, the proportion of fruit and
arthropods in fecal samples of Kirtland's warblers was consistent
(Wunderle et al. 2014, p. 25). Food abundance was a reliable predictor
of site fidelity, with birds shifting location to sites with higher
biomass of ripe fruit and ground arthropods during the late winter
(Wunderle et al. 2014, p. 31).
    The average life expectancy of adult Kirtland's warblers is
approximately 2.5
[[Page 54440]]
years (Walkinshaw 1983, pp. 142-143). The oldest Kirtland's warbler on
record was an 11-year-old male, which, when recaptured in the Damon
KWMA in 2005, appeared to be in good health and paired with a female
(USFS, unpubl. data).
    Overall, Kirtland's warbler annual survival estimates are similar
to those of other wood warblers (reviewed in Faaborg et al. 2010, p.
12). Survival rates of the Kirtland's warbler varied by sex and age
classes (Mayfield 1960, pp. 204-207; Walkinshaw 1983, pp. 123-143;
Bocetti et al. 2002, p. 99; Rockwell et al. 2017, p. 723; Trick,
unpubl. data). Based on mark-recapture data from 2006-2010 on breeding
grounds in Michigan and from 2003-2010 on the wintering grounds in The
Bahamas, the mean annual survival estimates for adults and yearlings
were 0.58 and 0.55, respectively (Rockwell et al. 2017, pp. 719-721).
Monthly survival probabilities were relatively high when birds were
stationary on the wintering and breeding grounds, and were
substantially lower during the migratory period, which has the highest
mortality rate out of any phase of the annual cycle, accounting for 44
percent of annual mortality (Rockwell et al. (2017, p. 722). Survival
probability was positively correlated to March rainfall in the previous
year, suggesting the effects of rain on the wintering grounds carried
over to affect annual survival in subsequent seasons. Late winter
rainfall in The Bahamas showed a positive effect on Kirtland's warblers
corrected body mass (Wunderle et al. 2014, p. 47). Reduced rain can
result in lower available food resources for Kirtland's warblers, which
could result in poorer body condition, making them less likely to
survive the subsequent spring migration (Rockwell et al. 2017, pp. 721-
722) and lowering reproductive success during the breeding season
(Rockwell et al. 2012, p. 745).
    Historically, one of the largest factors influencing Kirtland's
warbler's reproductive success was brood parasitism from brown-headed
cowbirds (Molothrus ater). Brown-headed cowbirds are obligate brood
parasites. Females remove an egg from a host species' nest and lay
their own egg to be raised by the adult hosts, usually resulting in the
death of the remaining host nestlings (Rothstein 2004, p. 375). Prior
to initiation of the brown-headed cowbird management program (discussed
in more detail under Factor E: Brood Parasitism), Kirtland's warblers
averaged less than one young fledged per nest (Walkinshaw 1983, p.
151). After brown-headed cowbird control efforts began in 1972, the
estimated number of chicks fledged per nest (1972 to 1977) increased to
2.67, with 63.3 percent nest success (Walkinshaw 1983, pp. 150-152).
More recently, mean annual reproductive success of 3.3 fledglings per
year per male has been observed (Rockwell et al. 2012, p. 748).
    From the information available, it appears that Kirtland's warblers
display winter and breeding-ground panmixia (mixing of individuals
across locations within the population). In 2007, eight birds examined
from six different wintering sites on Eleuthera Island were found on
breeding territories in the Damon KWMA in Ogemaw County, Michigan
(Ewert, unpubl. data). Additionally, four other birds banded from one
wintering site on Eleuthera Island were found on breeding territories
across four counties in northern lower Michigan. Kirtland's warblers
are also known to regularly move between KWMAs in northern lower
Michigan during the breeding season (Probst et al. 2003, p. 371).
Regardless of where they overwintered in The Bahamas (i.e., either Cat
or Eleuthera Islands), Kirtland's warblers intermixed heavily on the
breeding grounds and migrated to various sites throughout the breeding
range, showing a weak connectivity between the breeding and wintering
grounds (Cooper et al. 2018, pp. 5-6). These data suggest that the
warbler's population exhibits panmictic (a group of interbreeding
individuals where all individuals in the population are potential
reproductive partners) rather than metapopulation (groups of
interbreeding individuals that are geographically distinct) demographic
characteristics (Esler 2000, p. 368).
    Analysis of microsatellite DNA markers from Kirtland's warblers in
Oscoda County, Michigan, over three time periods (1903-1912, 1929-1955,
and 2008-2009) showed no evidence of a genetic bottleneck in the oldest
(1903-1912) sample, indicating that any population declines prior to
that point may have been gradual (Wilson et al. 2012, pp. 7-9).
Although population declines have been observed since then, there was
only weak genetic evidence of a bottleneck in the two more recent
samples (no bottleneck detected in two of three possible models for
each sample). The study showed a slight loss of allelic richness
between the oldest and more recent samples, but no significant
difference in heterozygosity between samples and no evidence of
inbreeding. Effective population size estimates varied depending on the
methods used, but none was low enough to indicate that inbreeding or
rapid loss of genetic diversity were likely in the future (Wilson et
al. 2012, pp. 7-9). Based on the available data, genetic diversity does
not appear to be a limiting factor for the Kirtland's warbler or
indicate the need for genetic management at this time.
Abundance and Population Trends
    Prior to 1951, the size of the Kirtland's warbler population was
extrapolated from anecdotal observations and knowledge about breeding
and wintering habitat conditions. The Kirtland's warbler population may
have peaked in the late 1800s, a time when conditions across the
species' distribution were universally beneficial (Mayfield 1960, p.
32). Wildfires associated with intensive logging, agricultural burning,
and railroads in the Great Lakes region burned hundreds of thousands of
acres, and vast portions were dominated by jack pine forests (Pyne
1982, pp. 199-200, 214). Suitable winter habitat consisting of low
coppice (early-successional and dense, broadleaf vegetation) was also
becoming more abundant, due to a decrease in widespread commercial
agriculture in The Bahamas after the abolition of slavery in 1834,
resulting in former croplands converting to scrub (low coppice) (Sykes
and Clench 1998, p. 245). During this time, Kirtland's warblers were
found in greater abundance throughout The Bahamas than were found in
previous decades, and reports of migratory strays came from farther
north and west of the known migratory range, evidence of a larger
population that would produce more migratory strays (Mayfield 1993, p.
    Between the early 1900s and the 1920s, agriculture in the northern
Great Lakes forests was being discouraged in favor of industrial tree
farming, and systematic fire suppression was integrated into State and
Federal policy (Brown 1999, p. 9). The estimated amount of jack pine on
the landscape suitably aged for Kirtland's warblers had decreased to
approximately 40,470 ha (100,000 ac) of suitable habitat in any one
year (Mayfield 1960, p. 26). This reduction in habitat presumably
resulted in fewer Kirtland's warblers from the preceding time period,
and Kirtland's warblers were not observed in all stands of suitable
conditions (Wood 1904, p. 10). Serious efforts to control forest fires
in Michigan began in 1927 and resulted in a further reduction of total
acres burned as the number and size of wildfires decreased (Mayfield
1960, p. 26; Radtke and Byelich 1963, p.
[[Page 54441]]
210). By this time, brown-headed cowbirds had expanded from the
shortgrass plains and become common within the Kirtland's warbler's
nesting range due to clearing of land for settlement and farming in
northern Michigan (Wood and Frothingham 1905, p. 49; Mayfield 1960, p.
146), further contributing to the decline of Kirtland's warblers.
    Figure: Kirtland's warbler census results for each year in which a
full census was completed (1951, 1961, 1971-2013, and 2015) (MDNR
data). Note: A rangewide census was not conducted in the years 1952-
1960, 1962-1970, 2014, or 2016-2018.
    Comprehensive surveys (censuses) of the entire Kirtland's warbler
population began in 1951. Because of the warbler's specific habitat
requirements and the frequent, loud, and persistent singing of
territorial males during the breeding season, it was possible to
establish a singing male census (Ryel 1976, pp. 1-2). The census
consists of an extensive annual survey of all known and potential
breeding habitat to count singing males.
    Censuses were conducted in 1951, 1961, each year from 1971 to 2013,
and 2015 (see figure, above). The 1951 census documented a population
of 432 singing males confined to 28 townships in eight counties in
northern lower Michigan (Mayfield 1953, p. 18). By 1971, the Kirtland's
warbler population declined to approximately 201 singing males and was
restricted to just 16 townships in six counties in northern lower
Michigan (Probst 1986, pp. 89-90). Over the next 18 years, the
Kirtland's warbler population level remained relatively stable at
approximately 200 singing males but experienced record lows of 167
singing males in 1974 and again in 1987. In response to conservation
efforts, including artificial regeneration of jack pine habitat (see
Breeding Habitat, above) and brown-headed cowbird trapping program, the
population of Kirtland's warbler began to increase dramatically
starting in the 1990s (see figure, above) and occupy a wider
distribution across the landscape. The population reached a record high
of 2,383 singing males in 2015, the year of the last full census (MDNR,
USFS, USFWS, unpubl. data).
    The census protocol counts singing males, not breeding pairs. Since
the census began, Kirtland's warbler conservation partners have often
made the assumption that there is a breeding female for each singing
male, so the number of singing males has often been used to approximate
the number of breeding pairs. Likewise, some reports estimate a total
breeding population by doubling the number of singing males.
Extrapolating from singing males to breeding pairs or total breeding
population should be done with caution. Mating success of males may
vary depending on the quality of habitat, method of regeneration, or
other factors (Bocetti 1994, pp. 80-85; Rockwell et al. 2013, p. 748;
Bocetti 2018, pers. comm.). The annual census provides a robust,
relative index of the Kirtland's warbler population change over time,
but results should not be interpreted as an absolute count (Probst et
al. 2005, pp. 50-59).
Population Viability
    Full annual cycle (breeding and wintering) dynamics were
incorporated into a population viability model to assess the long-term
population viability of the Kirtland's warbler under five management
scenarios: (1) Current suitable habitat and current brown-
[[Page 54442]]
headed cowbird removal; (2) reduced suitable habitat and current brown-
headed cowbird removal; (3) current suitable habitat and reduced brown-
headed cowbird removal, (4) current suitable habitat and no brown-
headed cowbird removal; and (5) reduced suitable habitat and reduced
brown-headed cowbird removal (Brown et al. 2017a, p. 443). The model
that best simulated recently observed Kirtland's warbler population
dynamics included a relationship between precipitation in the species'
wintering grounds and productivity (Brown et al. 2017a, pp. 442, 444),
which reflects our understanding of carry-over effects (Rockwell et al.
2012, pp. 748-750; Wunderle et al. 2014, pp. 46-48).
    Under the current management conditions scenario, which includes
habitat management at existing levels and brown-headed cowbird control
occurring throughout the northern Lower Peninsula of Michigan, the
model predicts that the Kirtland's warbler population will be stable
over a 50-year simulation period. When simulating a reduced brown-
headed cowbird removal effort by restricting cowbird trapping
activities to the central breeding areas in northern lower Michigan
(i.e., eastern Crawford County, southeastern Otsego County, Oscoda
County, western Alcona County, Ogemaw County, and Roscommon County) and
assuming a 41 percent or 57 percent reduction in Kirtland's warbler
productivity, the results showed a stable or slightly declining
population, respectively, over the 50-year simulation period (Brown et
al. 2017a, p. 447). Other scenarios, including reduced habitat
suitability and reduced Kirtland's warbler productivity due to
experimental jack pine management on 25 percent of available breeding
habitat, had similar results with projected population declines over
the 50-year simulation period, but mean population numbers remained
above the population goal of 1,000 pairs (Brown et al. 2017a, p. 446),
the numerical criterion identified in the Kirtland's warbler recovery
plan (USFWS 1985).
    Future reductions to Kirtland's warbler productivity rates under
two reduced cowbird removal scenarios were assumed to be similar to
historical rates (Brown et al. 2017a, p. 447). This assumption would
overestimate the negative effects on Kirtland's warbler productivity if
future parasitism rates are lower than the rates modeled (see Factor E:
Brood Parasitism, below, for additional information on contemporary
parasitism rates). Supplementary analysis (Brown et al. 2017b, unpubl.
report), using the model structure and assumptions of Brown et al.
(2017a), simulated the impacts of a 5, 10, 20, and 30 percent reduction
in productivity to take into consideration a wider range of possible
future parasitism rates. Even small reductions in annual productivity
had measurable impacts on population abundance, but there were not
substantial differences in mean population growth rate up to a 20
percent reduction in productivity (Brown et al. 2017b, p. 3). Even with
annual reductions in productivity of up to 5 percent for 50 years, the
population trend (growth rate) projected for the final 30 years of the
model simulations was 0.998 (range from the 5 simulations 0.993 to
1.007) or nearly the same as that projected in the simulations with no
reduction in productivity at 0.999 (range of 0.995 to 1.008) (Brown et
al. 2017b, p. 3). It is reasonable to infer that the Kirtland's warbler
population can support relatively small reductions in productivity over
a long period of time (e.g., the 50-year timeframe of the simulations),
providing a margin of assurance as management approaches are adaptively
managed over time, and the species may be able to withstand as much as
a 20 percent reduction in annual productivity, provided it does not
extend over several years.
    The results of the model simulations are more helpful in evaluating
the effect of various management decisions relative to one another,
rather than providing predictions of true population abundance. In
other words, the model output provides projections of relative trends,
rather than identifying specific population abundance thresholds.
Although there are limitations to all population models based on
necessary assumptions, input data limitations, and unknown long-term
responses such as adaptation and plasticity, data simulated by Brown et
al. (2017a and 2017b, entire) provide useful information in assessing
relative population trends for the Kirtland's warbler under a variety
of future scenarios and provide the best available analysis of
population viability.
    In summary, Kirtland's warbler population numbers have been greatly
affected by brown-headed cowbird parasitism rates and the extent and
quality of available habitat on the breeding grounds. The best
available population model predicts that limited non-traditional
habitat management and continued low brood parasitism rates will result
in sustained population numbers above the recovery goal. Monitoring
population numbers and brood parasitism rates will be important in
ensuring the Kirtland's warbler population remains stable post-
delisting (see Post-delisting Monitoring, below).
Recovery and Recovery Plan Implementation
    State and Federal efforts to conserve the Kirtland's warbler began
in 1957 and were focused on providing breeding habitat for the species.
The Kirtland's warbler was federally listed as an endangered species in
1967, under the Endangered Species Preservation Act of 1966 (Pub. L.
89-669). By 1972, a Kirtland's Warbler Advisory Committee formed to
coordinate management efforts and research actions across Federal and
State agencies, and conservation efforts expanded to include management
of brown-headed cowbird brood parasitism (Shake and Mattsson 1975, p.
    Efforts to protect and conserve the Kirtland's warbler were further
enhanced when the Endangered Species Act of 1973 became law and
provided for acquisition of land to increase available habitat, funding
to carry out additional management programs, and provisions for State
and Federal cooperation. In 1975, the Recovery Team was appointed by
the Secretary of the Interior to guide recovery efforts. A Kirtland's
Warbler Recovery Plan was completed in 1976 (USFWS 1976), and updated
in 1985 (USFWS 1985), outlining steps designed to protect and increase
the species' population.
    Recovery plans provide important guidance to the Service, States,
and other partners on methods of minimizing threats to listed species
and measurable objectives against which to measure progress towards
recovery, but they are not regulatory documents. A decision to revise
the status of or remove a species from the List is ultimately based on
an analysis of the best scientific and commercial data available to
determine whether a species is no longer an endangered species or a
threatened species, regardless of whether that information differs from
the recovery plan.
    The Kirtland's warbler recovery plan (USFWS 1985) identifies one
``primary objective'' (hereafter referred to as ``recovery criterion'')
that identifies when the species should be considered for removal from
the List, and ``secondary objectives'' (hereafter referred to as
``recovery actions'') that are designed to accomplish the recovery
criterion. The recovery criterion states that the Kirtland's warbler
may be considered recovered and considered for removal from the List
when a self-sustaining population has been re-established throughout
its known range at a minimum level of 1,000 pairs. The
[[Page 54443]]
1,000-pair goal was informed by estimates of the amount of the specific
breeding habitat required by each breeding pair of Kirtland's warblers,
the amount of potential habitat available on public lands in Michigan's
northern Lower Peninsula, and the ability of State and Federal land
managers to provide suitable nesting habitat on an annual basis. The
recovery criterion was intended to address the point at which the
ultimate limiting factors to the species had been ameliorated so that
the population is no longer in danger of extinction or likely to become
so within the foreseeable future.
    The recovery plan does not clearly articulate how meeting the
recovery criterion will result in a population that is at reduced risk
of extinction. The primary threats to the Kirtland's warbler are
pervasive and recurring threats, but threat-based criteria specifying
measurable targets for control or reduction of those threats were not
incorporated into the recovery plan. Instead, the recovery plan focused
on specific actions necessary to accomplish the recovery criterion.
These included managing breeding habitat, protecting the Kirtland's
warbler on its wintering grounds and along the migration route,
reducing key factors such as brown-headed cowbird parasitism from
adversely affecting reproduction and survival of Kirtland's warblers,
and monitoring the Kirtland's warbler to evaluate responses to
management practices and environmental changes.
    At the time the recovery plan was prepared, we estimated that land
managers would need to annually maintain approximately 15,380 ha
(38,000 ac) of nesting habitat in order to support and sustain a
breeding population of 1,000 pairs (USFWS 1985, pp. 18-20). We
projected that this would be accomplished by protecting existing
habitat, improving occupied and developing habitat, and establishing
approximately 1,010 ha (2,550 ac) of new habitat each year, across
51,640 ha (127,600 ac) of State and Federal pine lands in the northern
Lower Peninsula of Michigan (USFWS 1985, pp. 18-20). We also
prioritized development and improvement of guidelines that would
maximize the effectiveness and cost efficiency of habitat management
efforts (USFWS 1985, p. 24). The MDNR, USFS, and Service developed the
Strategy for Kirtland's Warbler Habitat Management (Huber et al. 2001,
entire) to update Kirtland's warbler breeding habitat management
guidelines and prescriptions based on a review of past management
practices, analysis of current habitat conditions, and new findings
that would continue to conserve and enhance the status of the
Kirtland's warbler (Huber et al. 2001, p. 2).
    By the time the recovery plan was updated in 1985, the brown-headed
cowbird control program had been in effect for more than 10 years. The
brown-headed cowbird control program had virtually eliminated brood
parasitism and more than doubled the warbler's productivity rates in
terms of fledging success (Shake and Mattsson 1975, pp. 2-4). The
Kirtland's warbler's reproductive capability had been successfully
restored, and the brown-headed cowbird control program was credited
with preventing further decline of the species. Because management of
brown-headed cowbird brood parasitism was considered essential to the
survival of the Kirtland's warbler, it was recommended that the brown-
headed cowbird control program be maintained for ``as long as
necessary'' (USFWS 1985, p. 27).
    Although the recovery plan identifies breeding habitat as the
primary limiting factor, with brood parasitism as a secondary limiting
factor, it also suggests that events or factors outside the breeding
season might be adversely affecting survival (USFWS 1985, pp. 12-13).
At the time the recovery plan was updated, little was known about the
Kirtland's warbler's migratory and wintering behavior, the species'
migratory and wintering habitat requirements, or ecological changes
that may have occurred within the species' migration route or on its
wintering range. This lack of knowledge emphasized a need for more
information on the Kirtland's warbler post-fledging, during migration,
and on its wintering grounds (Kelly and DeCapita 1982, p. 365).
Accordingly, recovery efforts were identified to: (1) Define the
migration route and locate wintering areas; (2) investigate the ecology
of the Kirtland's warbler and factors that might be affecting mortality
during migration and on its winter range; and (3) provide adequate
habitat and protect the Kirtland's warbler during migration and on its
wintering areas (USFWS 1985, pp. 24-26).
    In correspondence with the Service's Midwest Regional Director, and
based on more than 20 years of research on the Kirtland's warbler's
ecology and response to recovery efforts, the Recovery Team helped
clarify recovery progress and issues that needed attention prior to
reclassification to threatened status or delisting (Ennis 2002, pp. 1-
4; Ennis 2005, pp. 1-3). From that synthesis, several important
concepts emerged that continued to inform recovery, including: (1)
Breeding habitat requirements, amount, configuration, and distribution;
(2) brood parasitism management; (3) migratory connectivity and
protection of Kirtland's warblers and their habitat during migration
and on the wintering grounds; and (4) establishment of credible
mechanisms to ensure the continuation of necessary management (Thorson
2005, pp. 1-2).
    Our understanding of the Kirtland's warbler's breeding habitat
selection and use, and the links between maintaining adequate amounts
of breeding habitat and a healthy Kirtland's warbler population, has
continued to improve. As the population has rebounded, Kirtland's
warblers have become reliant on artificial regeneration of breeding
habitat, but have also recolonized naturally regenerated areas within
the historical range of the species and nested in habitat types
previously considered non-traditional or less suitable. As explained in
more detail below, recovery efforts have expanded to establish and
enhance management efforts on the periphery of the species' current
breeding range in Michigan's Upper Peninsula, Wisconsin, and Canada and
reflect the best scientific understanding of the amount and
configuration of breeding habitat (see Factor A discussion, below).
These adjustments improve the species' ability to adapt to changing
environmental conditions and to withstand stochastic disturbance and
catastrophic events, and better ensure long-term conservation for the
    Along with habitat management, brown-headed cowbird control has
proven to be a very effective tool in stabilizing and increasing the
Kirtland's warbler population. To ensure survival of the Kirtland's
warbler, we anticipate that continued brown-headed cowbird brood
parasitism management may be needed, at varying levels depending on
parasitism rates, to sustain adequate Kirtland's warbler productivity.
As explained in more detail below, brown-headed cowbird control
techniques and the scale of trapping efforts have adapted over time and
will likely continue to do so, in order to maximize program
effectiveness and feasibility (see Factor E: Brood Parasitism
discussion, below).
    We now recognize that the Kirtland's warbler persists only through
continual management activities designed to mitigate recurrent threats
to the species. The Kirtland's warbler is considered a conservation-
reliant species, which means that it requires continuing management to
address ongoing threats (Goble et al. 2012, p. 869). Conservation of
the Kirtland's warbler will continue
[[Page 54444]]
to require a coordinated, multi-agency approach for planning and
implementing conservation efforts into the future. Four elements that
should be in place prior to delisting a conservation-reliant species
include a conservation partnership capable of continued management, a
conservation plan, appropriate binding agreements (such as memoranda of
agreement (MOAs)) in place, and sufficient funding to continue
conservation actions into the future (Bocetti et al. 2012, p. 875).
    The Kirtland's warbler has a strong conservation partnership
consisting of multiple stakeholders that have invested considerable
time and resources to achieving and maintaining this species' recovery.
Since 2016, the Recovery Team is no longer active, but instead new
collaborative efforts formed to help ensure the long-term conservation
of the Kirtland's warbler regardless of its status under the ESA. These
efforts formed to facilitate conservation planning through
coordination, implementation, monitoring, and research efforts among
many partners and across the species' range. A coalition of
conservation partners lead by Huron Pines, a nonprofit conservation
organization based in northern Michigan, launched the Kirtland's
Warbler Initiative in 2013. The Kirtland's Warbler Initiative brings
together State, Federal, and local stakeholders to identify and
implement strategies to secure funds for long-term Kirtland's warbler
conservation actions given the continuous, recurring costs anticipated
with conserving the species into the future. The goal of this
partnership is to ensure the Kirtland's warbler thrives and ultimately
is delisted, as a result of strong public-private funding and land
management partnerships. Through the Kirtland's Warbler Initiative, a
stakeholder group called the Kirtland's Warbler Alliance was developed
to raise awareness in support of the Kirtland's warbler and the
conservation programs necessary for the health of the species and jack
pine forests.
    The second effort informing Kirtland's warbler conservation efforts
is the Kirtland's Warbler Conservation Team (KWCT). The KWCT was
established to preserve institutional knowledge, share information, and
facilitate communication and collaboration among agencies and partners
to maintain and improve Kirtland's warbler conservation. The current
KWCT is comprised of representatives from the Service, USFS, MDNR,
WDNR, U.S. Department of Agriculture's Wildlife Services (USDA-WS),
Canadian Wildlife Service, Huron Pines, Kirtland's Warbler Alliance,
The Nature Conservancy, and California University of Pennsylvania.
    Since 2015, conservation efforts for the Kirtland's warbler have
been guided by the Kirtland's Warbler Breeding Range Conservation Plan
(Conservation Plan) (MDNR et al. 2015, entire). The Conservation Plan
outlines the strategy for future cooperative Kirtland's warbler
conservation and provides technical guidance to land managers and
others on how to create and maintain Kirtland's warbler breeding
habitat within an ecosystem management framework. The scope of the
Conservation Plan currently focuses only on the breeding range of the
Kirtland's warbler within the United States, although the agencies
involved (MDNR, USFS, and USFWS; hereafter ``agencies'' or ``management
agencies'') intend to cooperate with other partners to expand the scope
of the plan in the future to address the entire species' range (i.e.,
the entire jack pine ecosystem, as well as the migratory route and
wintering range of the species). The Conservation Plan will be revised
every 10 years to incorporate any new information and the best
available science (MDNR et al. 2015, p. 1).
    In April 2016, the management agencies renewed a memorandum of
understanding (MOU) through December 31, 2020, committing to continue
collaborative habitat management, brown-headed cowbird control,
monitoring, research, and education in order to maintain the Kirtland's
warbler population at or above 1,000 breeding pairs, regardless of the
species' legal protection under the ESA (USFWS, MDNR, and USFS 2016,
entire). In addition, Kirtland's warbler conservation actions are
included in the USFS's Land and Resource Management Plans (Forest
Plans), which guide management priorities for the Huron-Manistee,
Hiawatha, and Ottawa National Forests.
    Funding mechanisms that support long-term land management and
brown-headed cowbird control objectives are in place to assure a high
level of certainty that the agencies can meet their commitments to the
conservation of the Kirtland's warbler. MDNR and USFS have replanted
approximately 26,420 ha (90,000 ac) of Kirtland's warbler habitat over
the past 30 years. Over the last 10 years, only a small proportion of
the funding used to create Kirtland's warbler habitat is directly tied
to the ESA through the use of grant funding (i.e., funding provided to
MDNR through the Service's section 6 grants to States' program).
Although there is the potential that delisting could reduce the
priority for Kirtland's warbler work within MDNR and USFS, as noted in
the Conservation Plan (MDNR 2015, p. 17), much of the forest management
cost (e.g., silvicultural examinations, sale preparation, and
reforestation) is not specific to maintaining Kirtland's warbler
breeding habitat and would likely be incurred in the absence of the
Kirtland's warbler. MDNR and USFS have successfully navigated budget
shortfalls and changes in funding sources over the past 30 years and
were able to provide sufficient breeding habitat to enable the
population to recover, and they have agreed to continue to do so
through the MOU. Additionally, the Service and MDNR developed an MOA to
set up a process for managing funds to help address long-term
conservation needs, specifically brown-headed cowbird control (USFWS
and MDNR 2015). If the annual income generated is greater than the
amount needed to manage brown-headed cowbird parasitism rates, the
remaining portion of the annual income may be used to support other
high priority management actions to directly benefit the Kirtland's
warbler, including wildlife and habitat management, land acquisition
and consolidation, and education. The MOA requires that for a minimum
of 5 years after the species is delisted, MDNR consult with the Service
on planning the annual brown-headed cowbird control program and other
high-priority actions. In addition, MDNR recently reaffirmed their
commitment to the MOA and confirmed their intent to implement and
administer the brown-headed cowbird control program, even if the
Kirtland's warbler is delisted (MDNR 2017).
    In summary, the general guidance of the recovery plan has been
effective, and the Kirtland's warbler has responded well to active
management over the past 50 years. The primary threats identified at
listing and during the development of the recovery plan have been
managed, and commitments are in place to continue managing the threats.
The status of the Kirtland's warbler has improved, primarily due to
breeding habitat and brood parasitism management provided by MDNR,
USFS, and the Service. The population has been above the 1,000 pair
goal since 2001, above 1,500 pairs since 2007, and above 2,000 pairs
since 2012. The recovery criterion has been met. Since 2015, efforts
for the Kirtland's warbler have been guided by a Conservation Plan that
will continue to be implemented by the management agencies when the
species is delisted.
[[Page 54445]]
    Since the revision of the recovery plan (USFWS 1985), decades of
research have been invaluable to refining recovery implementation and
have helped clarify our understanding of the dynamic condition of the
Kirtland's warbler, jack pine ecosystem, and factors influencing them.
The success of recovery efforts in mitigating threats to the Kirtland's
warbler are evaluated below.
Summary of Changes From the Proposed Rule
    Based upon our review of the comments received on the April 12,
2018, proposed rule (83 FR 15758), peer review comments, and new
information that became available since the publication of the proposed
rule, we reevaluated the information in the proposed rule and made
changes as appropriate. We made the following changes in this final
rule: (1) We added detail on the wintering distribution; (2) we
clarified that wintering habitat is broadleaf scrub rather than pine
habitat; (3) we added a paragraph on reproductive success; (4) we added
a discussion on anthropogenic disturbance regimes on the wintering
grounds; (5) we added information on connectivity between winter and
breeding grounds; (6) we clarified that census results (number of
singing males) are a relative index rather than an absolute count; (7)
we added a section on the effects of insects and disease to jack pine;
(8) we added a discussion of the effects of recreation; (9) we added a
discussion of pesticides; (10) we included new data on brown-headed
cowbird parasitism rates and the suspended trapping program during
2018; (11) we updated the analysis on effects of climate change on
breeding grounds; (12) we added a discussion of recent drought on the
wintering grounds; (13) we included new data on risk of heavy rainfall
events and extended period of hurricane force winds due to decreasing
translational speeds; and (14) we added a discussion of the effects of
hurricanes. In addition, we made efforts to improve clarity, improve
organization, and correct typographical or other minor errors. Many of
our edits were based on comments from peer reviewers and public
comments; additional detail can be found under Summary of Comments and
Recommendations, below.
Summary of Factors Affecting the Kirtland's Warbler
    Section 4 of the ESA and its implementing regulations (50 CFR part
424) set forth the procedures for listing species, reclassifying
species, or removing species from listed status. The term ``species''
includes ``any subspecies of fish or wildlife or plants, and any
distinct population segment [DPS] of any species of vertebrate fish or
wildlife which interbreeds when mature'' (16 U.S.C. 1532(16)). A
species may be determined to be an endangered species or threatened
species because of any one or a combination of the five factors
described in section 4(a)(1) of the ESA: (A) The present or threatened
destruction, modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence. We must consider these same five
factors in delisting a species. We may delist a species according to 50
CFR 424.11(d) if the best available scientific and commercial data
indicate that the species is neither endangered nor threatened for one
or more of the following reasons: (1) The species is extinct; (2) the
species has recovered and is no longer endangered or threatened; or (3)
the original scientific data used at the time the species was
classified were in error.
    For species that are already listed as endangered or threatened,
this analysis of threats is an evaluation of both the threats currently
facing the species and the threats that are reasonably likely to affect
the species in the foreseeable future following delisting or
downlisting (i.e., reclassification from endangered to threatened) and
the removal or reduction of the ESA's protections. A recovered species
is one that no longer meets the ESA's definition of endangered or
threatened. A species is ``endangered'' for purposes of the ESA if it
is in danger of extinction throughout all or a ``significant portion of
its range'' and is ``threatened'' if it is likely to become endangered
within the foreseeable future throughout all or a ``significant portion
of its range.'' The word ``range'' in the ``significant portion of its
range'' phrase refers to the range in which the species currently
exists. For the purposes of this analysis, we will evaluate whether the
Kirtland's warbler should be considered endangered or threatened
throughout all of its range. Then we will consider whether there are
any significant portions of the Kirtland's warbler's range where the
species is in danger of extinction or likely to become so within the
foreseeable future.
    The ESA does not define the term ``foreseeable future.'' For the
purpose of this rule, we define the ``foreseeable future'' to be the
extent to which, given the amount and substance of available data, we
can anticipate events or effects, or reliably extrapolate threat
trends, such that we reasonably believe that reliable predictions can
be made concerning the future as it relates to the status of the
Kirtland's warbler. We used the anticipated habitat and brown-headed
cowbird management analyzed over a 50-year timeframe in Brown et al.
(2017a, b) to define the foreseeable future for the Kirtland's warbler.
This analysis considered multiple future management scenarios for
Kirtland's warbler, including reduced suitable habitat (from
experimental habitat management) and reduced brown-headed cowbird
removal. Given the length of time for habitat to become suitable and
the warbler's average life span, a 50-year period takes into account
multiple rotations of habitat and generations of birds. This is a
sufficient amount of time to fully evaluate if the current and
potential future experimental approaches to management warrant further
refinement. Beyond 50 years, the future conditions become more
uncertain, such that we cannot make reliable predictions as to how any
differing management scenarios may affect the status of the species.
    In considering what factors might constitute threats, we must look
beyond the exposure of the species to a particular factor to evaluate
whether the species may respond to the factor in a way that causes
actual impacts to the species. If there is exposure to a factor and the
species responds negatively, the factor may be a threat, and during the
status review, we attempt to determine how significant a threat it is.
The threat is significant if it drives or contributes to the risk of
extinction of the species, such that the species warrants listing as
endangered or threatened as those terms are defined by the ESA.
However, the identification of factors that could impact a species
negatively may not be sufficient to compel a finding that the species
warrants listing. The information must include evidence sufficient to
suggest that the potential threat is likely to materialize and that it
has the capacity (i.e., it should be of sufficient magnitude and
extent) to affect the species' status such that it meets the definition
of endangered or threatened under the ESA. The following analysis
examines all five factors currently affecting or that are likely to
affect the Kirtland's warbler in the foreseeable future.
[[Page 54446]]
A. The Present or Threatened Destruction, Modification, or Curtailment
of Its Habitat or Range
Breeding Habitat
    Historically, wildfires were the most important factor in the
establishment of natural jack pine forests and Kirtland's warbler
breeding habitat. However, modern wildfire suppression greatly altered
the natural disturbance regime that generated Kirtland's warbler
breeding habitat for thousands of years (USFWS 1985, p. 12; Cleland et
al. 2004, pp. 316-318). Prior to the 20th century, the historic fire
recurrence in jack pine forests averaged 59 years, but it is now
estimated to occur in cycles as long as 775 years (Cleland et al. 2004,
pp. 315-316).
    In the absence of wildfire, land managers must take an active role
in mimicking natural processes that regularly occurred within the jack
pine ecosystem, namely stand-replacing disturbance events. This is
primarily done through large-scale timber harvesting and human-assisted
reforestation. Although planted stands tend to be more structurally
simplified than wildfire-regenerated stands (Spaulding and Rothstein
2009, p. 2610), land managers have succeeded in selecting KWMAs that
have landscape features of the natural breeding habitat and have
developed silvicultural techniques that produce conditions within
planted stands suitable for Kirtland's warbler nesting. In fact, over
85 percent of the habitat used by breeding Kirtland's warblers in 2015
in the northern Lower Peninsula of Michigan (approximately 12,343 ha
(30,500 ac)) had been artificially created through clearcut harvest and
replanting. The planted stands supported over 92 percent of the
warbler's population within the Lower Peninsula during the 2015
breeding season (MDNR, USFS, USFWS, unpubl. data). The effectiveness of
these strategies is also evident by the reproductive output observed in
planted stands, which function as population sources (Bocetti 1994, p.
95). Thus, in a landscape where natural fire disturbance patterns have
been reduced, threats to natural breeding habitat are being mitigated
through large-scale habitat management. Therefore, the status of the
Kirtland's warbler depends largely on the continued production of
managed breeding habitat.
    Federal and State laws establish the foundation for managing the
USFS, USFWS, and MDNR lands that provide the majority of the breeding
habitat for Kirtland's warbler. These laws require land management
agencies to develop plans that describe objectives and goals for forest
    The National Forest Management Act (16 U.S.C. 1600-1640; NFMA)
requires that Forest Plans shall ``provide for multiple use and
sustained yield of the products and services . . . and, in particular,
include coordination of outdoor recreation, range, timber, watershed,
wildlife and fish, and wilderness'' (16 U.S.C. 1604(e)). All projects
and activities authorized by the Forest Service must be consistent with
the established Forest Plans (16 U.S.C. 1604(i)). The Hiawatha, Huron-
Manistee, and Ottawa National Forest Plans include specific goals and
objectives for maintaining Kirtland's warbler breeding habitat (USFS
2006a, p. 35; USFS 2006b, p. 82; USFS 2006c, p. 27). The NFMA's
implementing regulations will apply to any future Forest Plan revisions
and currently require National Forests to develop plans that include
standards or guidelines to maintain or restore the ecological integrity
of terrestrial ecosystems in the plan area (36 CFR 219.8(a)). Further,
additional species-specific standards or guidelines may be required to
maintain a viable population of each species of conservation concern
within the plan area (36 CFR 219.9(b)(1)). The Forest Service plans to
designate Kirtland's warbler as a Sensitive Species upon delisting for
a period of at least five years (Hogeboom 2019, pers. comm.).
Additionally, in accordance with the Forest Service Manual (FSM), any
significant current or predicted downward trends in population numbers,
density, or in habitat capability that would reduce a species' existing
distribution would be triggers for the Regional Forester to designate
the Kirtland's warbler as a Sensitive Species (FSM 2670.5) in the
future. Forest Service objectives for Sensitive Species (FSM 2670.22)
include developing and implementing management practices to ensure that
species do not become threatened or endangered because of Forest
Service actions.
    The National Wildlife Refuge System Improvement Act of 1997
requires the preparation of Comprehensive Conservation Plans for refuge
lands and maintenance of the biological integrity, diversity, and
environmental health of the National Wildlife Refuge System. The
Service's Kirtland's Warbler Wildlife Management Area defines goals,
objectives, and strategies that support Kirtland's warbler and the jack
pine ecosystem (USFWS 2009, pp. 31-33).
    In Michigan law, Part 525, Sustainable Forestry on State Forest
Lands, of the Natural Resources and Environmental Protection Act (1994
PA 451, as amended) requires the MDNR to manage the State forest lands
consistent with the principles of sustainable forestry. Part 525 also
requires the MDNR to maintain third-party certification of the
management of the State forest that satisfies sustainable forestry
standards. The MDNR forest lands are certified under the standards of
the Forest Stewardship Council and the Sustainable Forestry Initiative
(Kintigh 2019, pers. comm.). These standards also require the MDNR to
write, implement, and maintain forest management plans. The MDNR has
developed a Regional State Forest Management Plan for the northern
Lower Peninsula ecoregion that includes specific plans for 15 units of
land managed for Kirtland's warbler (MDNR 2013, pp. 337-354). The
Federal and State forest management planning standards, which will
remain in effect after delisting, are synthesized and further refined
for Kirtland's warbler through the Conservation Plan (MDNR et al.
    The Conservation Plan (MDNR et al. 2015) identifies continued
habitat management needs and objectives to maintain sufficient suitable
breeding habitat for Kirtland's warblers. Habitat management is
currently conducted on approximately 88,626 ha (219,000 ac) of jack
pine forest within MDNR, USFS, and Service lands throughout the
northern Lower Peninsula and Upper Peninsula of Michigan (MDNR et al.
2015, pp. 22-23). The Conservation Plan incorporates some conservative
assumptions about the area needed to support a breeding pair of
Kirtland's warblers, as well as how long a stand will be used by the
species. The density and duration of use estimates were developed by
data gathered over the last decade. Lands within the Lower Peninsula
averaged 8 to 9 ha (19 to 22 ac) per pair and had a duration of use
between 9 and 10 years. Lands within the Upper Peninsula on the
Hiawatha National Forest required an average of 40 ha (100 ac) per pair
and had a duration of use averaging 10 years (Huber et al. 2013, cited
in MDNR et al. 2015, p. 22). Using those measures of average hectares
per pair and duration of use, 14,593 ha (36,060 ac) of suitable
breeding habitat would need to be available at all times to maintain a
minimum population of 1,300 pairs, requiring land management agencies
to jointly manage 1,550 ha (3,830 ac) of habitat annually (631 ha
(1,560 ac) on MDNR land and 918 ha (2,270 ac) on USFS land) through
[[Page 54447]]
regenerated jack pine or managed reforestation (MDNR et al. 2015, pp.
22-23). Importantly, the more recent observations concerning density of
Kirtland's warblers in breeding habitat and duration of stand use are
often greater than the assumptions used for planning purposes and
explain why the Kirtland's warbler population that is actually observed
is higher than would be predicted based on the planning assumptions.
    As described previously, the majority of managed breeding habitat
is currently created through clear cutting and planting jack pine
seedlings. However, managing jack pine for Kirtland's warbler breeding
habitat typically results in lower value timber products due to the
overall poor site quality in combination with the required spacing,
density, and rotation age of the plantings (Greco 2017, pers. comm.).
Furthermore, the demand for jack pine products has fluctuated in recent
years, and long-term forecasts for future marketability of jack pine
are uncertain. Commercially selling jack pine timber on sites where
reforestation will occur is critical to the habitat management program.
Timber receipts offset the cost of replanting jack pine at the
appropriate locations, scales, arrangements, and densities needed to
support a viable population of nesting Kirtland's warblers that would
not otherwise be feasible through conservation dollars. The
Conservation Plan directs management agencies to develop at least 75
percent of the Kirtland's warbler's breeding habitat annual acreage
objectives using traditional habitat management techniques (i.e.,
opposing wave planting with interspersed openings), and no more than 25
percent of annual acreage objectives should use non-traditional habitat
management techniques (e.g., reduced stocking density, incorporating a
red pine component within a jack pine stand, prescribed burning) (MDNR
et al. 2015, p. 23). Using non-traditional techniques on a maximum of
25 percent of breeding habitat acreage annually will allow the
management agencies to evaluate new planting methods that improve
timber marketability, reduce costs, and improve recreational
opportunities while sustaining the warbler's population above the
recovery criterion of 1,000 pairs. The KWCT is currently working on
developing additional habitat regeneration techniques through adaptive
management that increase the marketability of the timber at harvest
while not substantially reducing Kirtland's warbler habitat suitability
(Kennedy 2017, pers. comm.).
    The land management agencies have maintained adequate breeding
habitat despite times when their budgets were flat or declining, even
while costs related to reforestation continued to increase. For
example, over the last 30 years, MDNR replanted more than 20,000 ha
(50,000 ac) of Kirtland's warbler habitat, averaging over 680 ha (1,700
ac) per year. They took this action voluntarily, and within the past 10
years, they used funding from sources in addition to those available
under the ESA. Section 6 grants under the ESA have helped support
MDNR's Kirtland's warbler efforts, but that funding has largely been
used for population census work in recent years and reflects only a
small percentage of the funding the State of Michigan spends annually
to produce Kirtland's warbler breeding habitat. Other funding sources
used by MDNR include State wildlife grants, competitive State wildlife
grants, Michigan's Nongame Fund, and the Forest Development Fund.
    Shifting agency priorities and competition for limited resources
have and will continue to challenge the ability of land managers to
fund reforestation of areas suitable for Kirtland's warblers. Low jack
pine timber sale revenues, in conjunction with reduced budgets,
increased Kirtland's warbler habitat reforestation costs, and
competition with other programs, are all challenges that the land
management agencies have met in the past and will need to continue
addressing to meet annual habitat development objectives. Commitments
by land managers and the KWCT are in place, as described earlier in
this document, to ensure recovery of the Kirtland's warbler will be
sustained despite these challenges.
    The management agencies have agreed through the Conservation Plan
(MDNR et al. 2015, pp. 24, 43-44) to generally limit or prohibit
commercial, recreational, or infrastructure (e.g., roads, pipelines,
communication towers) development within or near areas managed for
Kirtland's warbler to protect them and provide for the long-term
integrity of breeding habitat. Additionally, a regulatory mechanism
that aids in the management of breeding habitat is Executive Order
(E.O.) 13186, ``Responsibilities of Federal Agencies to Protect
Migratory Birds'' (66 FR 3853; January 17, 2001), which directs Federal
agencies to develop a memorandum of understanding (MOU) with the
Service to promote the conservation of migratory bird populations. USFS
and the Service signed an MOU (FS Agreement #08-MU-1113-2400-264),
pursuant to E.O. 13186, with the purpose of strengthening migratory
bird conservation by identifying and implementing strategies that
promote conservation and avoid or minimize adverse impacts on migratory
birds through enhanced collaboration.
    Once planted for Kirtland's warbler habitat, jack pine trees need
to survive to provide usable habitat. Multiple natural events, such as
fire, drought, disease, and insect outbreaks, may affect the survival
of jack pine trees and longevity of suitable habitat. Wildfire can be
harmful to Kirtland's warblers when it destroys occupied habitat. For
example, on May 18, 2010, a wildfire started in southeastern Crawford
County within the Eldorado KWMA. The wildfire eventually burned a total
of approximately 3,071 ha (7,588 ac), including 146 ha (362 ac) of
occupied habitat (where 30 singing males were counted in 2009) and 36
ha (90 ac) of young jack pine habitat that would have likely been
occupied by Kirtland's warblers in 3 years (USFS 2010, pp. 1, 7, 11).
The following year on June 7, 2011, lightning ignited a wildfire that
destroyed approximately 49 ha (120 ac) of 11-year-old habitat in the
Manistee River KWMA, where seven male Kirtland's warblers were counted
during the 2011 census (MDNR, unpubl. data). Drought can cause
mortality of jack pine seedlings (Rajasekaran and Blake 1999, p. 175)
and reduce the density of jack pine trees (Kintigh 2011, pers. comm.).
Drought can also stress older jack pines and make them more susceptible
to insects and diseases (Kintigh 2011, pers. comm.). Fungal pests,
including Gremmeniella abietina var. abietina, and Sphaeropsis sapinea
(also known as Diplodia pinea), are known to cause mortality in jack
pine trees (USFS and MDNR 1981, p. 14; Nicholls and Ostry 1990, p. 55).
Jack pine budworm (Choristoneura pinus pinus), mountain pine beetle
(Dendroctonus ponderosae), and jack pine sawfly (Neodiprion swainei)
can also cause topkill and mortality in jack pine trees (McCullough
2000, p. 252; Colgan and Erbilgin 2011, p. 426; Wilson 1971, p. 1).
Generally, past impacts of these natural events on jack pines have had
little effect on Kirtland's warbler habitat. Severe outbreaks of insect
or fungal pests can have devastating effects on large areas of forest
(e.g., the effect of emerald ash borer (Agrilus planipennis Fairmaire)
on ash species (Fraxinus spp.)). Although there are no known imminent
threats to Kirtland's warbler, emerging disease and pests warrant
continued monitoring
[[Page 54448]]
because of the potential to harm significant amounts of managed
habitat. Jack pine forests that serve as Kirtland's warbler habitat are
under the oversight of forest-management agencies that closely track
new forest diseases and pests and will take swift action if a newly
emerging issue is detected.
    We reviewed available information on the effects to Kirtland's
warbler habitat from expanded development on private lands in or near
breeding habitat. Although these factors and forest pests and diseases
have the potential to affect Kirtland's warblers and their habitat,
land management agencies have been successful in maintaining sufficient
amounts of suitable habitat to support historically high numbers of
Kirtland's warblers. While activities and natural processes (e.g.,
wildfire, drought, development) that affect breeding habitat may still
have some negative effects on individual Kirtland's warblers, the
population of Kirtland's warblers appears resilient to these factors
within the context of the current management regime. Furthermore,
management efforts to date have been adaptive in terms of the acreage
and spatial and temporal configuration of habitat needed to mitigate
the effects associated with natural breeding habitat loss and
fragmentation. The land management agencies have shown a commitment to
Kirtland's warbler habitat management through their forest management
plans as reflected in the 2016 MOU, agreeing to continue habitat
management, and developing and implementing the Conservation Plan.
Migration Habitat
    Although Kirtland's warblers spend a relatively small amount of
time each year migrating, the migratory period has the highest
mortality rate of any phase of the annual cycle, accounting for 44
percent of annual mortality (Rockwell et al. 2017, p. 722). Migratory
survivorship levels are, however, above the minimum needed to sustain
the population (Mayfield 1960, pp. 204-207; Berger and Radabaugh 1968,
p. 170; Bocetti et al. 2002, p. 99; Rockwell et al. 2017, pp. 721-723;
Trick, unpubl data). Recent research is refining our knowledge of
spring and fall migration timing and routes for the Kirtland's warbler.
Little is currently known about the importance of specific stopover
sites and any factors affecting them, although coastal areas along the
Great Lakes and Atlantic Ocean (e.g., western Lake Erie basin and the
Florida and Georgia coasts) that appear important to migrating
Kirtland's warblers are also areas where natural habitats have been
highly fragmented by human development. At stopover sites within these
highly fragmented landscapes, competition for food sources among long-
distance passerine migrants is expected to be high, especially in
fallout areas where many migrating birds land to rest, usually due to
weather events or long flights over open water (Moore and Yong 1991,
pp. 86-87; Kelly et al. 2002, p. 212; N[eacute]meth and Moore 2007, p.
373). Increased competition may prolong stopover duration or increase
the number of stopovers that are needed to complete migration between
breeding and wintering grounds (Goymann et al. 2010, p. 480).
    The quantity and quality of migratory habitat needed to sustain
Kirtland's warbler numbers above the recovery goal of 1,000 pairs
appears to be sufficient, based on a sustained and increasing
population since 2001. If loss or destruction of migratory habitat were
limiting or likely to limit the population to the degree that
maintaining a healthy population may be at risk, it should be apparent
in the absence of the species from highly suitable breeding habitat in
the core breeding range. In fact, we have seen just the opposite:
Increasing densities of breeding individuals in core areas and a range
expansion into what would appear to be less suitable habitat elsewhere.
This steady population growth and range expansion has occurred despite
increased development and fragmentation of migratory stopover habitat
within coastal areas.
Wintering Habitat
    Similar to the breeding grounds, the quantity and quality of
wintering habitat needed to sustain Kirtland's warbler numbers above
the recovery goal of 1,000 pairs appears to be sufficient, based on a
sustained and increasing population since 2001. Compared to the
breeding grounds, less is known about the wintering grounds in The
Bahamas. Factors affecting Kirtland's warblers on the wintering
grounds, as well as the magnitude of the impacts, remain somewhat
uncertain. Few of the known Kirtland's warbler wintering sites
currently occur on protected land. Rather, most Kirtland's warblers
appear to winter more commonly in early successional habitats that have
recently been or are currently being used by people (e.g., abandoned
after clearing, grazed by goats), where disturbance has set back plant
succession (Wunderle et al. 2010, p. 132). Potential threats to
wintering habitat include habitat loss caused by human development,
altered fire regime, changes in agricultural practices, and invasive
plant species. The potential threats of rising sea level, drought, and
destructive weather events, such as hurricanes on the wintering
grounds, are discussed below under Factor E.
    Tourism is the primary economic activity in The Bahamas, accounting
for 65 percent of the gross domestic product, and The Bahamas' Family
Islands Development Encouragement Act of 2008 supports the development
of resorts on each of the major Family Islands (part of The Bahamas)
(Moore and Gape 2009, p. 72). Residential and commercial development
could result in direct loss of Kirtland's warbler habitat, especially
on New Providence and Grand Bahama, which together support 85 percent
of the population of Bahamian people (Moore and Gape 2009, p. 73;
Wunderle et al. 2010, p. 135; Ewert 2011, pers. comm.). This loss could
occur on both private and commonage lands (land held communally by
rural settlements), as well as generational lands (lands held jointly
by various family members).
    Local depletion and degradation of the water table from wells and
other water extraction and introduction of salt water through human-
made channels or other disturbances to natural hydrologies may also
negatively impact Kirtland's warblers by affecting fruit and arthropod
availability (Ewert 2011, pers. comm.).
    Fire may have positive or negative impacts on winter habitat,
depending on the frequency, timing, and intensity of fires and where
the fires occur. Fires are relatively common and widespread on the pine
islands in the northern part of the archipelago and have increased
since settlement, especially during the dry winter season when
Kirtland's warblers are present (The Nature Conservancy 2004, p. 3).
Fire may benefit Kirtland's warblers when succession of low coppice to
tall coppice is set back (Currie et al. 2005b, p. 79) but may
negatively impact wintering Kirtland's warblers if it results in
reduced density and fruit production of understory shrubs (Currie et
al. 2005b, p. 85).
    Invasive plants are another potential factor that could limit the
extent of winter habitat in The Bahamas. Brazilian pepper (Schinus
terebinthifolius), jumbie bean (Leucaena leucocephala), Guinea grass
(Panicum maximum), and Casuarina or Australian pine (Casuarina
equisetifolia) may be the most important invasive species of immediate
concern (Ewert 2011, pers. comm.; Wunderle 2018, pers. comm.). These
aggressive plants colonize patches early after disturbances and may
form monocultures, which preclude the establishment of fruit plant
species heavily used by Kirtland's
[[Page 54449]]
warblers. Casuarina pine establishment can increase sand loss by out-
competing native plants that stabilize dunes, resulting in increased
coastal erosion and habitat loss (Sealey 2011, p. 12).
    Some invasive species, such as jumbie bean, are good forage for
goats. By browsing on these invasive plants, goats create conditions
that favor native shrubs and may increase the density of native shrubs
used by Kirtland's warblers (Ewert 2011, pers. comm.). Goat farming
could play a role in controlling the spread of some invasive species at
a local scale, while aiding in the restoration of native vegetation
patches. Still, many plants such as royal poinciana (Delonix regia),
tropical almond (Terminalia catappa), and morning glory (Ipomoea
indica) are commonly imported for landscaping and have the potential to
escape into the wild (Smith 2010, pp. 9-10; Ewert 2011, pers. comm.)
and could displace native shrubs that provide fruit for Kirtland's
    The Bahamas National Trust administers 32 national parks that cover
more than 809,371 ha (2 million ac) (Bahamas National Trust 2017, p.
3). Although not all national parks contain habitat suitable for
Kirtland's warblers, several parks provide suitable wintering habitat,
including the Leon Levy Native Plant Preserve on Eleuthera Island,
Harrold and Wilson Ponds National Park on New Providence Island, and
Exuma Cays Land and Sea Park on Hawksbill Cay (The Nature Conservancy
2011, p. 2).
    The Bahamas National Trust Act of 1959 and the National Parks
Ordinance of 1992 established non-government statutory roles to the
Bahamas National Trust and the Turks and Caicos Islands National Trust,
respectively. These acts empower these organizations to hold and manage
environmentally important lands in trust for their respective
    Simply protecting parcels of land or important wintering habitat,
however, may be insufficient to sustain adequate amounts of habitat for
the Kirtland's warbler because of the species' dependence on early
successional habitat (Mayfield 1972, p. 349; Haney et al. 1998, p. 210;
Sykes and Clench 1998, pp. 256-257; Wunderle et al. 2010, p. 124),
which changes in distribution over time. In addition, food availability
at any one site varies seasonally, as well as between years, and is not
synchronous across all sites (Wunderle et al. 2010, p. 124). In the
face of changes in land use and availability, sustaining sufficient
patches of early-successional habitat for Kirtland's warbler in The
Bahamas will likely require a landscape-scale approach (Wunderle et al.
2010, p. 135).
    Although threats to Kirtland's warblers on the wintering grounds
exist as a result of habitat loss due to succession or development,
hydrology changes, fire, and invasive species, the current extent and
magnitude of these threats appears not to be significantly limiting
Kirtland's warbler population numbers based on the species' continuous
population growth over the last two decades.
Habitat Distribution
    The Kirtland's warbler has always occupied a relatively limited
geographic range on both the breeding and wintering grounds. This
limited range makes the species naturally more vulnerable to
catastrophic events compared to species with wide geographic
distributions, as having multiple populations in a wider distribution
reduces the likelihood that all individuals will be affected
simultaneously by a catastrophic event (e.g., large wildfire in
breeding habitat, hurricane in The Bahamas). Since the species was
listed, the geographic area where the Kirtland's warbler occurs has
increased, reducing the risk to the species from catastrophic events.
As the population continues to increase and expand in new breeding and
wintering areas, the species will become less vulnerable to
catastrophic events. The Conservation Plan, which land management
agencies agreed to implement under the 2016 MOU, includes a goal to
improve distribution of habitat across the breeding range to reduce
this risk by managing lands in the Upper Peninsula of Michigan and in
Wisconsin in sufficient quantity and quality to provide breeding
habitat for 10 percent (100 pairs) or more of the goal of 1,000 pairs
(MDNR et al. 2015, p. 23).
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
    The Kirtland's warbler is a non-game species, and no commercial
harvest is known to occur in either the breeding or wintering grounds.
Land management agencies within the Kirtland's warbler's breeding range
previously had, and will continue to have, the ability to implement
seasonal closures to specific areas for a variety of reasons and, when
necessary, could limit access outside of designated roads and trails to
further protect the species. Within the 23 KWMAs in the northern Lower
Peninsula of Michigan and designated lands in Michigan's Upper
Peninsula, approximately 71 km (44 miles) of routes are designated for
off-road vehicle (ORV), all-terrain vehicle (ATV), or motorcycle use.
In addition, approximately 151 km (94 miles) of trails are designated
for hiking, biking, and horseback riding (USFWS, unpubl. data).
Additionally, approximately 3,510 km (2,181 miles) of authorized
ungraded and graded roads occur within the KWMAs (USFWS, unpubl. data).
As described in the Conservation Plan (MDNR et al. 2015, p. 16),
existing forest roads and trails have not typically been closed or
otherwise restricted specifically because of the presence of adjacent
Kirtland's warbler habitat.
    On a few occasions (Enger 2007, pers. comm.; Kaiser 2014, pers.
comm.), motor vehicles used on roads open to such use have collided
with and killed Kirtland's warblers. In addition, the noise from roads
has been shown to reduce breeding success of other passerines
(Schroeder et al. 2012, pp. 6-7; Proppe et al. 2013, pp. 1080-1082) and
could have similar negative effects to Kirtland's warblers. Any past
direct and indirect effects of road use have not hindered progress
toward recovering the Kirtland's warbler, however, and we do not
anticipate a greater extent of effects related to recreation post-
delisting. Because Kirtland's warblers occupy large blocks of habitat
over long periods of time (Donner et al. 2010, p. 5), maintaining
larger areas of habitat is a primary management goal (MDNR 2015, pp.
33-34). Managing for larger blocks of breeding habitat reduces the
effects of roads and trails that are on the edges of the habitat
    A variety of State, national, and international laws protect
Kirtland's warblers independent of their status under the ESA. Laws
outside of the U.S. played an important role in helping to recover the
species, and State laws will in some cases provide additional
protections after delisting. The Kirtland's warbler is protected by the
Migratory Bird Treaty Act of 1918 (MBTA; 16 U.S.C. 703-712). The MBTA
prohibits take, capture, killing, trade, or possession of Kirtland's
warblers and their parts, as well as their nests and eggs. The
regulations implementing the MBTA further define ``take'' as to
``pursue, hunt, shoot, wound, kill, trap, capture, or collect'' or
attempt those activities (50 CFR 10.12).
    The States of Florida, Georgia, Indiana, Michigan, North Carolina,
Ohio, Virginia, and Wisconsin list the Kirtland's warbler as
endangered, under their respective State endangered species
regulations. In Michigan, where the majority of the population breeds,
part 365 of Public Act 451 of 1994 prohibits take, possession,
[[Page 54450]]
transportation, importation, exportation, processing, sale, offer for
sale, purchase, or offer to purchase, transportation or receipt for
shipment by a common or contract carrier of Kirtland's warblers or
their parts.
    The Kirtland's warbler was declared federally endangered in Canada
in 1979. Canada's Species at Risk Act of 2003 (SARA) is the primary law
protecting the Kirtland's warbler in Canada. SARA bans killing,
harming, harassing, capturing, taking, possessing, collecting, buying,
selling, or trading of individuals that are federally listed. SARA also
extends protection to the residence (habitat) of individuals that are
federally listed. In addition, the Kirtland's warbler is listed as
endangered under Ontario's Endangered Species Act of 2007. Canada's
Migratory Bird Convention Act of 1994 also provides protections to
Kirtland's warblers. Under Canada's Migratory Bird Convention Act, it
is unlawful to be in possession of migratory birds or nests, or to buy,
sell, exchange, or give migratory birds or nests, or to make them the
subject of commercial transactions.
    In The Bahamas and the Turks and Caicos Islands, the Kirtland's
warbler is recognized as a globally ``Near Threatened'' species but has
no federally listed status. In The Bahamas, the Wild Birds Protection
Act (chapter 249) allows the Minister of Wild Animals and Birds
Protection to establish and modify reserves for the protection of any
wild bird. The species is also protected in The Bahamas by the Wild
Animals (Protection) Act (chapter 248) that prohibits the take or
capture, export, or attempt to take, capture, or export any wild animal
from The Bahamas. The Bahamas regulates scientific utilization of the
Kirtland's warbler, based on recommendations previously provided by the
Kirtland's Warbler Recovery Team (Bocetti 2011, pers. comm.).
    Through the MBTA, SARA, laws in The Bahamas, and State laws, the
species remains protected from pursuit, wounding, or killing that could
potentially result from activities focused on the species in breeding,
wintering, and migratory habitat (e.g., wildlife photography without
appropriate care to ensure breeding birds can continue to feed and care
for chicks and eggs normally and without injury to their offspring).
C. Disease or Predation
    There is no information of any disease impacting the Kirtland's
    For most passerines, nest predation has the greatest negative
impact on reproductive success and can affect entire populations
(Ricklefs 1969, p. 6; Martin 1992, p. 457). Nest predation may be
particularly detrimental for ground-nesting bird species in shrublands
(Martin 1993, p. 902). Predation rates of Kirtland's warbler nests have
ranged from 3 to 67 percent of nests examined (Mayfield 1960, p. 204;
Cuthbert 1982, p. 1; Walkinshaw 1983, p. 120); however, few predation
events have been directly observed, and, in general, evidence regarding
the importance of certain nest or adult predators lack quantitative
support (Mayfield 1960, p. 182; Walkinshaw 1972, p. 5; Walkinshaw 1983,
pp. 113-114).
    Overall, nest predation rates for Kirtland's warblers are similar
to other passerines and are below levels that would compromise
population replacement (Bocetti 1994, pp. 125-126; Cooper et al.,
unpubl. data). The increasing numbers of domestic cats (Felis catus) in
the breeding and wintering habitats is recognized (Lepczyk et al. 2003,
p. 192; Horn et al. 2011, p. 1184), but there is not sufficient
evidence to conclude at this time that predation from cats is currently
having population-level impacts to the Kirtland's warbler.
D. Inadequacy of Existing Regulatory Mechanisms
    Under this factor, we examine the threats identified within the
other factors as ameliorated or exacerbated by any existing regulatory
mechanisms or conservation efforts. Section 4(b)(1)(A) of the ESA
requires that the Service take into account ``those efforts, if any,
being made by any State or foreign nation, or any political subdivision
of a State or foreign nation, to protect such species.'' In relation to
Factor D under the ESA, we interpret this language to require the
Service to consider relevant Federal, State, and Tribal laws,
regulations, and other such binding legal mechanisms that may
ameliorate or exacerbate any of the threats we describe in threat
analyses under the other four factors or otherwise enhance the species'
conservation. Our consideration of the regulatory mechanisms addressing
the threats to the species, is described where applicable in the
relevant factor section (see discussion under Factors A, B, and E).
E. Other Natural or Manmade Factors Affecting Its Continued Existence
    Pesticides have the potential to cause direct and indirect effects
to non-target species, but we are not aware of any pesticides that are
negatively affecting the Kirtland's warbler population. Kirtland's
warblers could be exposed to pesticides on the breeding or wintering
grounds or during migration. On the breeding grounds, forest managers
are not routinely using any pesticides within occupied jack pine stands
(Huber 2018, pers. comm.; Kintigh 2018, pers. comm.). For Kirtland's
warbler, exposure to pesticides would be most likely through dietary
exposure (treatment of insects or fruit plants) or accidental spray
drift on the edges of suitable habitat.
    The U.S. Environmental Protection Agency used Kirtland's warbler as
a case study during the re-registration process for two organophosphate
pesticides, chlorpyrifos and malathion (Moore et al. 2017, p. 1). A
probabilistic model was developed to assess the risks of the two
pesticides to the birds during the breeding season and migration. The
model results predicted very low acute and chronic risk for these
pesticides for Kirtland's warbler (Moore et al. 2017, p. 265). This
conclusion is unsurprising, as Moore et al. (2017, p. 267) found that
treatments do not occur on Kirtland's warbler breeding grounds and only
rarely would warblers be exposed during migration.
Brood Parasitism
    Brood parasitism can depress reproduction of avian hosts in several
ways, including the direct removal or predation of eggs or young,
facilitating nest predation by other nest predators, reducing hatching
or fledging success, altering host population sex ratios, and
increasing juvenile and adult mortality beyond the nest (Elliot 1999,
p. 55; Hoover 2003, pp. 928-929; Smith et al. 2003, pp. 777-780;
Zanette et al. 2005, p. 818; Hoover and Reetz 2006, pp. 170-171; Hoover
and Robinson 2007, p. 4480; Zanette et al. 2007, p. 220).
    The brown-headed cowbird is the only obligate brood parasite within
the Kirtland's warbler's breeding range and the only species documented
parasitizing Kirtland's warbler nests. Two facultative interspecific
nest parasite species, the black-billed cuckoo (Coccyzus
erythropthalmus) and the yellow-billed cuckoo (Coccyzus americanus),
may occur within the Kirtland's warbler's breeding range, but
parasitism of a Kirtland's warbler nest has not been documented for
these species and is not believed to be a threat.
    Although brown-headed cowbirds were historically restricted to
prairie ecosystems, forest clearing and agricultural development of
Michigan's Lower Peninsula in the late 1800s
[[Page 54451]]
facilitated the brown-headed cowbird's range expansion into Kirtland's
warbler nesting areas (Mayfield 1960, p. 145) such that brown-headed
cowbirds were common within the Kirtland's warbler's breeding range by
the early 1900s (Wood and Frothingham 1905, p. 49). The first known
instance of brood parasitism of a Kirtland's warbler nest occurred in
Crawford County, Michigan, in 1908 (Strong 1919, p. 181). Shortly
thereafter, the scarcity of Kirtland's warblers was attributed to
brown-headed cowbird parasitism (Leopold 1924, p. 57), which later data
confirmed as significantly affecting the survival of the Kirtland's
warbler (Mayfield 1960, pp. 180-181).
    The Kirtland's warbler is particularly sensitive to brown-headed
cowbird brood parasitism. The warbler's limited breeding range likely
exposes the entire population to brown-headed cowbird parasitism
(Mayfield 1960, pp. 146-147; Trick, unpubl. data). In addition, the
peak egg-laying period of the brown-headed cowbird completely overlaps
with that of the Kirtland's warbler, and the majority of Kirtland's
warblers produce only one brood each year (Mayfield 1960, pp. 151-152;
Radabaugh 1972, p. 55; Rockwell, unpubl. data). Kirtland's warblers
have limited evolutionary experience with brown-headed cowbirds
compared to other hosts and have not developed effective defensive
behaviors to thwart brood parasitism (Walkinshaw 1983, pp. 157-158).
    Between 1903 and 1971, observed parasitism rates of Kirtland's
warbler nests ranged from 48 percent to 86 percent (reviewed in Shake
and Mattson 1975, p. 2). Brown-headed cowbirds also appear to exert
greater pressure on Kirtland's warbler nests than other passerines
within the same breeding habitat, with 93 percent of brown-headed
cowbird eggs found in jack pine habitat placed in Kirtland's warbler
nests compared to all other host species combined (Walkinshaw 1983, p.
154). Kirtland's warbler fledging rates averaged less than one young
per nest prior to the initiation of brown-headed cowbird control
(Walkinshaw 1972, p. 5).
    The effect of brown-headed cowbird parasitism exacerbated negative
impacts associated with habitat loss in the decline of the Kirtland's
warbler population (Rothstein and Cook 2000, p. 7). Once trapping of
brown-headed cowbirds within Kirtland's warbler nesting areas was
demonstrated to decrease parasitism rates and increase Kirtland's
warbler nesting success (Cuthbert 1966, pp. 1-2), intensive brown-
headed cowbird removal was recommended on major Kirtland's warbler
nesting areas as one of the necessary steps for the recovery of the
Kirtland's warbler (Shake and Mattsson 1975, p. 2).
    Starting in 1972, the Service, in conjunction with the USDA-WS,
MDNR, and USFS, implemented an intensive brown-headed cowbird control
program within Kirtland's warbler nesting areas in Michigan's Lower
Peninsula. On average, the control program annually removes
approximately 3,573 brown-headed cowbirds from occupied Kirtland's
warbler habitat in northern lower Michigan (USDA-WS 2016, unpubl.
report). Recent trap rates, however, have been below 1,500 brown-headed
cowbirds per year (USDA-WS, unpubl. data).
    Following the initiation of brown-headed cowbird control in
northern lower Michigan in 1972, brood parasitism rates decreased to
6.2 percent, and averaged 3.4 percent between 1972 and 1981 (Kelly and
DeCapita 1982, p. 363). Kirtland's warbler fledging rates
simultaneously increased from less than one per nest to 2.8 per nest,
and averaged 2.78 young fledged per nest between 1972 and 1981 (Kelly
and DeCapita 1982, pp. 364-365). Had brown-headed cowbird parasitism
not been controlled, the Kirtland's warbler population may have been
reduced to only 42 pairs by 1974 (Mayfield 1975, p. 43).
    Brood parasitism of Kirtland's warbler nests also occurs in
Wisconsin, and brown-headed cowbird trapping is conducted in select
Kirtland's warbler breeding areas. The trapping program in Wisconsin
started in 2008, and is run using similar methods to the program in
Michigan, with an average of 238 brown-headed cowbirds captured per
year (USDA-WS, USFWS unpubl. data). In 2007, two of three Kirtland's
warbler nests were parasitized (USFWS, unpubl. data). After the
initiation of brown-headed cowbird control in 2008, brood parasitism
rates in Wisconsin have fluctuated substantially among years, from 10
percent to 66 percent (USFWS, unpubl. data; Trick, unpubl. data).
However, in the same time period (2008-2017), overall nest success has
ranged from 19 to 80 percent, and the average fledge rate was estimated
to be between 1.51 to 1.92 chicks per nest (USFWS 2017, pp. 2-3).
    Limited studies on the effectiveness of the brown-headed cowbird
control program in relation to Kirtland's warbler nest productivity in
Michigan have been conducted since the early 1980s. Brown-headed
cowbirds were nearly eliminated in areas directly adjacent to a trap,
and brown-headed cowbird densities increased 5 km (3 miles) and greater
from brown-headed cowbird removal areas (De Groot and Smith 2001, p.
877). Brown-headed cowbird densities also significantly increased at
distances greater than 10 km (6 miles) from brown-headed cowbird
removal areas, further demonstrating the localized effect of brown-
headed cowbird control (De Groot and Smith 2001, p. 877). Although
brown-headed cowbird density increased with distance beyond 5 km (3
miles) of brown-headed cowbird traps, brown-headed cowbird densities
were still low in those areas compared to other parts of North America
(De Groot and Smith 2001, p. 877). Anecdotal observations of brood
parasitism rates within Kirtland's warbler nesting areas during periods
of brown-headed cowbird control indicated very low levels of brood
parasitism; parasitism rates have been reduced to less than 1 percent
of all nests in areas where trapping occurred (Bocetti 1994, p. 96;
Rockwell 2013, pp. 80, 93; Rockwell, unpubl. data).
    A study is currently underway in Michigan to evaluate the effective
range of a brown-headed cowbird trap and to determine the brood
parasitism rate of Kirtland's warbler nests when traps are not operated
during the warbler's breeding season. Beginning in 2015, 12 brown-
headed cowbird traps (out of 55 total) were closed for two breeding
seasons. In 2015, only one nest out of 157 was parasitized,
approximately 4.6 km (2.9 miles) away from the nearest brown-headed
cowbird trap. In 2016, similar low rates of parasitism were observed,
with only 2 parasitized nests out of 128. Due to the low levels of
brood parasitism observed, an additional 6 traps were closed in 2017,
and none of the 100 nests observed between 0.5 and 22.1 km (0.3 and
13.7 miles) from a brown-headed cowbird trap in 2017 were parasitized
(Cooper et al., unpubl. data). In total, only 3 of 385 Kirtland's
warbler nests were parasitized in areas with a spatially reduced
trapping program from 2015 to 2017. These preliminary data corroborate
similar findings that the effective range of a brown-headed cowbird
trap is likely much larger than the range (i.e., 1.6 km (1 mile)
radius) traditionally used in planning and implementing the brown-
headed cowbird control program. Following these results, all brown-
headed cowbird trapping in Michigan's northern Lower Peninsula was
suspended for the 2018 nesting season. Only 1 of 129 Kirtland's warbler
nests was found to be
[[Page 54452]]
parasitized (Cooper et al., unpubl. data) in 2018.
    Trend estimate data from Breeding Bird Survey routes between 2005
and 2015 show decreasing brown-headed cowbird populations in Michigan
and the Upper Great Lakes (Sauer et al. 2017, p. 169). Reduced brown-
headed cowbird abundance within Kirtland's warbler nesting areas is
supported by results from point count surveys conducted between 2015
and 2018 in Kirtland's warbler nesting areas in Michigan's northern
Lower Peninsula where brown-headed cowbird traps were not being
operated. Only 67 brown-headed cowbirds were observed during 1,134
point count surveys (Cooper et al., unpubl. data).
    However, in similar experiments where brown-headed cowbird trapping
was reduced or brought to an end following a lengthy period of
trapping, brood parasitism rates elevated or returned to pre-trapping
rates. Research at Fort Hood Military Reservation in Texas showed that
after 3 years of decreased brown-headed cowbird trapping levels,
parasitism rates increased from 7.9 percent to 23.1 percent and
resulted in black-capped vireo (Vireo atricapilla) nest survival
decreasing to unsustainable levels (Kostecke et al. 2009, p. 1). Other
studies have found similar results with parasitism frequency and host
bird productivity returning to pre-trapping levels quickly upon
discontinuing cowbird removal (Kosciuch and Sandercock 2008, p. 546).
    After 45 years of brown-headed cowbird trapping in Michigan, the
threat of brood parasitism on the Kirtland's warbler has been greatly
reduced but not eliminated. Brown-headed cowbirds remain present, but
potentially in lower numbers, in jack pine habitat away from brown-
headed cowbird traps, even if that area had been trapped in previous
years (DeGroot and Smith 2001, p. 877; Bailey 2007, pp. 97-98; Cooper
et al., unpubl. data). Female brown-headed cowbirds are highly
prolific, estimated to produce up to 40 eggs in a breeding season
(Scott and Ankney 1980, p. 680). Successful brown-headed cowbird
reproduction outside of trapped areas may maintain a population of
adult brown-headed cowbirds that could return in subsequent years with
the ability to parasitize Kirtland's warbler nests. It is unclear if
reduced parasitism rates are a permanent change to the landscape of
northern lower Michigan. The best available information, however,
indicates that cowbird removal efforts can be reduced, at least
temporarily, without adversely impacting Kirtland's warbler
productivity rates. Given the historical impact that the brown-headed
cowbird has had on the Kirtland's warbler, and the potential for the
brown-headed cowbird to negatively affect the warbler, a sustainable
Kirtland's warbler population depends on monitoring the magnitude and
extent of brood parasitism and subsequently adjusting the level of
cowbird trapping appropriately.
    The MOA (see Recovery and Recovery Plan Implementation, above)
established in 2015 between the Service and MDNR addresses the
commitment and long-term costs associated with future efforts to
control brown-headed cowbirds. The MOA established a dedicated account
from which income can be used to implement cowbird management and other
conservation actions for the Kirtland's warbler. To date, the account
has greater than $2.1 million invested for long-term growth. The MDNR
has re-confirmed their commitment to implement and administer the
brown-headed cowbird management program once the species is delisted
(MDNR 2017). Given our understanding of the status of brown-headed
cowbirds in northern lower Michigan, the $2.1 million investment,
coupled with the MDNR's commitment, is sufficient to provide an
effective brown-headed cowbird management program into the foreseeable
Climate Change
    Our analyses under the ESA include consideration of ongoing and
projected changes in climate. A recent compilation of climate change
and its effects is available from reports of the Intergovernmental
Panel on Climate Change (IPCC) (IPCC 2014, entire). In our analyses, we
use our expert judgment to weigh relevant information, including
uncertainty, in our consideration of various aspects of climate change.
    The effects of climate change on Kirtland's warblers were not
identified as a threat to the species in the listing rule (32 FR 4001;
March 11, 1967) or in the updated recovery plan (USFWS 1985, entire).
Potential effects of climate change to the Kirtland's warbler could
occur as a result of changes on the breeding or wintering grounds and
include a decrease and shift in suitable breeding habitat outside of
the species' current range (Prasad et al. 2007, unpaginated), increase
in pests or pathogens of jack pine, a decrease in the extent of
wintering habitat, and decoupling of the timing of migration from food
resource peaks that are driven by temperature and are necessary for
migration and feeding offspring (van Noordwijk et al. 1995, p. 456;
Visser et al. 1998, pp. 1869-1870; Thomas et al. 2001, p. 2598; Strode
2003, p. 1142).
    Breeding Grounds: On the breeding grounds, climate change
projections, based on low (B1) and high (A1FI) emission scenarios,
predict shifts in mean temperature and precipitation as well as altered
timing and extremes (Handler et al. 2014, pp. 68-84; Janowiak et al.
2014, pp. 66-85; GLISA 2018, unpaginated). In the core breeding area,
temperatures are expected to increase across all seasons, with more
dramatic increases during winter months (Handler et al. 2014, p. 72).
Precipitation is projected to increase in winter and spring but may
decrease in the summer (Handler et al. 2014, pp. 73-75), with more
extreme precipitation events representing a larger proportion of the
total annual and seasonal rainfall (Handler et al. 2014, p. 82).
    The extent and availability of suitable Kirtland's warbler habitat
within jack pine forests on the breeding grounds could change based on
projected changes to temperature and precipitation. The Forest
Service's Forest Ecosystem Vulnerability Assessments considered impacts
to above-ground biomass for 26 tree species, and projected stable (in
Wisconsin) or slight reductions (in Michigan) in the biomass of jack
pine over the next 50 years, with more significant declines projected
by the end of the 21st century (Handler et al. 2014, p. 94; Janowiak et
al. 2014, p. 99). In addition to a possible reduction in the biomass of
jack pine, the spatial distribution of the species may also shift in
response to changing climate.
    The projections of how jack pine will be affected by climate change
vary based on the model used and emission scenario considered. Overall,
models predict that jack pine occurrence will contract in the northern
Lower Peninsula and shift out of peripheral breeding areas. Scenarios
using both low (B1) and high (A1F1) greenhouse gas emissions predicted
a reduction of the extent of jack pine in Michigan but an expansion of
jack pine in western Wisconsin and Minnesota (Prasad et al. 2007,
unpaginated). More recent models using emission scenarios with
Representative Concentration Pathways (RCPs) of 4.5 and 8.5 similarly
projected a decline in jack pine occurrence in Michigan and indicated
declines in northern Minnesota, northern Wisconsin, and the Upper
Peninsula of Michigan (Donner et al. 2018, pp. 270-273). However,
conditions were projected to remain suitable for jack pine occupancy in
northern lower Michigan (Donner et al. 2018, pp. 271).
[[Page 54453]]
    Insect pests may become more problematic to jack pine under future
climatic changes, with increasing damage and spread of new jack pine
pests in the Kirtland's warbler's habitat areas. A warmer climate may
increase the susceptibility of current jack pine forests to damage from
pests and diseases (Bentz et al. 2010, pp. 606-610; Cudmore et al.
2010, pp. 1040-1042; Safranyik et al. 2010, p. 432) and may allow for
new pests such as western bark beetle to arrive (Handler et al. 2014,
p.130). Forest managers will continue to monitor pest and pathogen
outbreaks in jack pine forests.
    Competition with deciduous forest species is also expected to favor
an expansion of the deciduous forest into the southern portions of the
boreal forest (USFWS 2009, p. 14) and affect interspecific
relationships between the Kirtland's warbler and other wildlife
(Colwell and Rangel 2009, p. 19657; Wiens et al. 2009, p. 19729).
However, warmer weather and increased levels of carbon dioxide could
also lead to an increase in tree growth rates on marginal forestlands
that are currently temperature-limited (NAST 2000, p. 57). Higher air
temperatures will cause greater evaporation and, in turn, reduce soil
moisture, resulting in conditions conducive to forest fires (NAST 2000,
p. 57) that favor jack pine propagation. Too much change in the fire
regime could have a negative effect on jack pine regeneration and
result in a shift to barrens (Handler et al. 2014, p. 130).
Additionally, warmer temperatures could also lead to greater moisture
stress, through accelerated litter layer decomposition leading to lower
water-holding capacity (Handler et al. 2014, p. 130). Alternatively,
warmer conditions and longer growing seasons could benefit pine
forests, if carbon dioxide fertilization boosts long-term water-use
efficiency and productivity (Handler et al. 2014, pp. 102, 114-115,
    Recent vulnerability analyses estimate moderate potential impacts
to jack pine forests as a result of the effects of climate change and
low-moderate adaptive capacity of jack pine, based on its high
tolerance for disturbance and existing management practices (Handler et
al. 2014, p. 130). A climate change vulnerability assessment for
wildlife species by MDNR (Hoving et al. 2013, p. 40), using
NatureServe's Climate Change Vulnerability Index, categorized
Kirtland's warbler as ``Presumed Stable,'' with the caveat that while
the population may remain stable, its range may shift outside of
    In summary, there may be a reduction or a shift in available
suitable jack pine habitat over the next 50 years, but these reductions
may be offset to some degree by other ecosystem processes, such as an
altered fire regime and adaptive habitat management (harvest of jack
pines and techniques, such as the use of containerized saplings rather
than bare-root stock, for planting jack pine plantations). Jack pine
may also adapt to changing climatic conditions. As suitable habitat
shifts, Kirtland's warblers could also adapt by utilizing more marginal
habitat, or increasing in density in high-quality habitat. The KWCT
will continue to analyze the extent and distribution of suitable
habitat, and the effects of pests and disease on jack pine.
    Wintering Grounds: On the wintering grounds, effects of climate
change to the Kirtland's warbler could occur as a result of changing
temperature and precipitation, rising sea levels, and storm events. For
migratory species, unfavorable changes on the wintering grounds can
result in subsequent negative effects on fitness later in the annual
life cycle (Marra et al. 1998, p. 1885; Sillett et al. 2000, pp. 2040-
2041; Rockwell et al. 2012, pp. 747-748; Rockwell et al. 2017, p. 721).
For the Kirtland's warbler, wintering habitat condition affects
survival and reproduction (Rockwell et al. 2012, pp. 747-748; Rockwell
et al. 2017, p. 721). These effects likely result from limited resource
availability on the wintering grounds that reduces body condition and
fat reserves necessary for successful migration and reproduction
(Wunderle et al. 2014, pp. 47-49). The availability of sufficient food
resources is affected by the amount of habitat for arthropods and
fruiting plants, temperature, and precipitation (Brown and Sherry 2006,
pp. 25-27; Wunderle et al. 2014, p. 39).
    Temperatures in the Caribbean have shown strong warming trends
across all regions, particularly since the 1970s (Jones et al. 2016,
pp. 3325, 3332), and are likely to continue to warm. A climate model
with a high emission scenario (A2) predicted an increase in temperature
of almost 2.5 to 3.0 degrees Celsius (4.5 to 6.3 degrees Fahrenheit)
above the mean temperatures of 1970-1989 by the 2080s (Karmalkar et al.
2013, p. 301). Climate change models using a lower emissions scenario
(RCP4.5) project an increase in surface temperature in the Caribbean
ranging from 1.2 to 1.9 degrees Celsius (2.2 to 3.4 degrees Fahrenheit)
for 2081-2100 when compared to 1986-2005 (Nurse et al. 2014, p. 1628).
Other models, using high (A2) and low (B2) emission scenarios, also
predicted an increase in the number of warm days and nights and a
decrease in the frequencies of cool days and nights, in addition to
higher mean daily temperatures, for 2071-2099 relative to 1961-1999
(Stennett-Brown et al. 2017, pp. 4838-4840). Increased temperatures
could affect food availability by altering food supply (arthropod and
fruit availability), although it is unknown to what extent the
predicted increases in temperature would increase or decrease food
supply for the Kirtland's warbler. Other effects of increasing
temperature related to sea level and precipitation are described below.
    Increasing temperatures can contribute to sea level rise from the
melting of ice over land and thermal expansion of seawater. A wide
range of estimates for future global mean sea level rise is found in
the scientific literature (Church et al. 2013, entire; IPCC 2013a,
entire; Simpson et al. 2010, pp. 55-61; Sweet et al. 2017, entire). By
2070, global mean sea level is projected to increase by 0.35 m (1.15
ft) to 0.42 m (1.38 ft) under RCP4.5 and RCP8.5 scenarios (IPCC 2013a,
p. 1445). Another model predicts increases in sea level ranging from
0.35 m (1.15 ft) to 0.79 m (2.59 ft) by 2070 under comparable emission
scenarios (Sweet et al. 2017, p. 23). An increase in sea level could
reduce the availability of suitable habitat due to low-elevation areas
being inundated, resulting in a reduction in the size of the islands on
which Kirtland's warblers winter (Amadon 1953, p. 466; Dasgupta et al.
2009, pp. 21-23). The Bahamas archipelago is mainly composed of small
islands, and more than 80 percent of the landmass is within 1.5 m (4.9
ft) of mean sea level (The Bahamas Environment, Science and Technology
Commission 2001, p. 43). This makes The Bahamas particularly vulnerable
to future rises in sea level (Simpson et al. 2010, p. 74), which could
result in a reduction of the extent of winter habitat and negatively
impact the Kirtland's warbler. Estimates of total landmass loss
throughout The Bahamas due to a 1-meter (3.3 ft) rise in sea level vary
from 5 percent (Simpson et al. 2010, p. 77) to 11 percent (Dasgupta et
al. 2007, p. 12; 2009, p. 385). However, not all of the land that may
be inundated is potentially suitable for Kirtland's warbler (e.g.,
developed land, closed-canopy forest). To assess how climate change
scenarios may affect Kirtland's warbler's wintering habitat, we
considered a recent estimate of potential Kirtland's warbler habitat
loss due to sea level rise (Wolcott et al. 2018, entire). Loss of open-
land habitat varied across the archipelago, based on elevational
differences (Wolcott et al. 2018, p. 10). There have historically
[[Page 54454]]
been few observations of Kirtland's warblers on the northern islands
(Cooper et al. 2019, p. 84), where elevations are lower and where
projections indicate the greatest loss of open land (Wolcott et al.
2018, p. 10). On Eleuthera, the island with the greatest known density
of overwintering Kirtland's warblers, a rise in sea level of 1 meter
(3.3 ft) or 2 meters (6.6 ft) would result in a loss of potential
Kirtland's warbler wintering habitat of 0.8 percent and 2.6 percent,
respectively (Wolcott et al. 2018, p. 9). Given that the projected rise
in sea level in the foreseeable future is less than 1 meter (3.3 ft),
we anticipate the loss of potential Kirtland's warbler winter habitat
on Eleuthera due to sea level rise will be less than 0.8 percent.
    Generally, climate models predict a drying trend in the Caribbean,
but there is considerable temporal and spatial variation and often
disagreement among models regarding specific predictions that make it
difficult to determine the extent to which reduced rainfall or timing
of rainfall may affect the Kirtland's warbler in the future. We
reviewed available literature examining precipitation trends and
projections in the Caribbean, and specifically The Bahamas, to assess
the potential effects of changes in precipitation.
    Precipitation patterns in the Caribbean from 1979 to 2012 did not
show statistically significant century-scale trends across regions, but
there were periods of up to 10 years when some regions were drier or
wetter than the long-term averages (Jones et al. 2016, p. 10). In the
northern Caribbean (which includes The Bahamas, Cuba, Jamaica, Haiti,
Dominican Republic, and Puerto Rico), some years were more wet than the
average, and other years were more dry across all seasons (Jones et al.
2016, p. 3314), with higher precipitation totals since about 2000.
Within The Bahamas, precipitation trends during the dry season
(November through April) showed a significant drying trend for 1979-
2009 (Jones et al. 2016, pp. 3328, 3331).
    Model projections under two emission scenarios (RCP4.5 and 8.5)
found that the projected precipitation varied seasonally and spatially
throughout the islands of The Bahamas, both in the mid-term (2050) and
long-term (2100) (Wolcott et al. 2018, pp. 4-6). The northern and
north-central islands are likely to have increased precipitation in
March (compared to baseline conditions), whereas the central islands
are likely to become drier (Wolcott et al. 2018, p. 7-8) under both
emission scenarios, with the magnitude of projected changes greater in
    Accurately projecting future precipitation trends in the Caribbean
is difficult due to the complex interactions between sea surface
temperatures, atmospheric pressure at sea level, and predominant wind
patterns. Further, some models have difficulty accurately simulating
the semi-annual seasonal cycle of precipitation observed in the
Caribbean (Karmalkar et al. 2013, pp. 300-302). Recent models using
statistical downscaling techniques have improved resolution but still
show limitations for predicting precipitation (Stennett-Brown et al.
2017, p. 4840). Thus, rainfall projections where Kirtland's warblers
overwinter have limited certainty and should be interpreted with
caution. Understanding the likely projected precipitation in The
Bahamas and Caribbean is important because of the strong link between
late winter rainfall and fitness of Kirtland's warblers. A drying trend
on the wintering grounds will likely cause a corresponding reduction in
available food resources (Studds and Marra 2007, pp. 120-121; Studds
and Marra 2011, pp. 4-6). Rainfall in the previous month was an
important factor in predicting fruit abundance (both ripe and unripe
fruit) for wild sage and black torch in The Bahamas (Wunderle et al.
2014, p. 19), which is not surprising given the high water content (60-
70 percent) of their fruit (Wunderle, unpubl. data, cited in Wunderle
et al. 2014, p. 4). Carry-over effects of weather on the wintering
grounds, particularly late-winter rainfall, have been shown to affect
spring arrival dates, reproductive success, and survival rates of
Kirtland's warblers (reviewed in Wunderle and Arendt 2017, pp. 5-12;
Rockwell et al. 2012, p. 749; Rockwell et al. 2017, pp. 721-722).
    Decreases in rainfall and resulting decreases in food availability
may also result in poorer body condition prior to migration. The need
to build up the necessary resources to successfully complete migration
could, in turn, result in delays to spring departure in dry years
(Wunderle et al. 2014, p. 16) and may explain observed delays in
arrival times following years with less March rainfall in The Bahamas
(Rockwell et al. 2012, p. 747). Delays in the spring migration of
closely related American redstarts (Setophaga ruticilla) have also been
directly linked to variation in March rainfall and arthropod biomass
(Studds and Marra 2007, p. 120; Studds and Marra 2011, p. 4), and have
also resulted in fewer offspring produced per summer (Reudink et al.
2009, p. 1624). These results strongly indicate that environmental
conditions modify the timing of spring migration, which likely carries
a reproductive cost. If The Bahamas experience a significant winter
drying trend, Kirtland's warblers may be pressured to delay spring
departures, while simultaneously contending with warming trends in
their breeding range that pressure them to arrive earlier in the
spring. Projection population modeling (Rockwell et al. 2017, p. 2)
estimated a negative population growth in Kirtland's warbler as a
result of a reduction of more than 12.4 percent from the current mean
levels in March rainfall.
    A recent drought in the Caribbean from 2013 to 2016, due in part to
El Ni[ntilde]o, resulted in some of the highest temperatures and
potential evapotranspiration anomalies observed in the region (Herrera
and Ault 2017, p. 7822). As a result, it has been characterized as the
most severe drought in the region since at least 1950 (Herrera and Ault
2017, p. 7822) and may have been appreciably more severe because of
anthropogenic warming (i.e., 15 to 17 percent of the drought's severity
and approximately 7 percent of its spatial extent could be attributed
to the anthropogenic effects of climate change) (Herrera et al. 2018,
pp. 4-5). Future droughts are predicted to be increasingly severe
because of higher temperatures, which played an important role in the
2013-2016 drought, regardless of changes in precipitation (Herrera et
al. 2018, p. 7). For the period during and following the 2013-2016
drought, the Kirtland's warbler population remained stable or
increased, indicating at least some level of resilience to severe,
short-term drought.
    Extreme weather events, such as tropical storms and hurricanes,
will continue to occur with an expected reduction in the overall
frequency of weaker tropical storms and hurricanes and an increase in
the frequency of the most intense hurricanes (category 4 and 5
hurricanes), based on several dynamical climate-modeling studies of
Atlantic basin storm frequency and intensity (Bender et al. 2010, p.
456; Knutson et al. 2010, pp. 159-161; Murakami et al. 2012a, pp. 2574-
2576; Murakami et al. 2012b, pp. 3247-3253; Knutson et al. 2013, pp.
6599-6613; Knutson et al. 2015, pp. 7213-7220). Although very intense
hurricanes are relatively rare, they inflict a disproportionate impact
in terms of storm damage (e.g., approximately 93 percent of damage
resulting from hurricanes is caused by only 10 percent of the storms
(Mendelsohn et al. 2012,
[[Page 54455]]
p. 3)). An increasing trend for hurricanes to have decreased forward or
translational speeds may increase the future risk of heavy rainfall
events and extended period of hurricane-force winds over an island
(Kossin 2018, p. 105). This could result in future increased risks to
Kirtland's warblers and their winter habitat.
    Hurricanes have the potential to result in direct mortality of
Kirtland's warblers during migration and while on the wintering grounds
(Mayfield 1992, p. 11), but most birds do not arrive in The Bahamas
until mid-October to early November, after peak hurricane season
(Wunderle and Ewert 2018, p. 1). There is a high risk of short-term
effects following the hurricane due to altered shelter and food (Wiley
and Wunderle 1993, pp. 331-336). During recent observations of
hurricane effects on the island of San Salvador, post-hurricane
declines of Kirtland's warblers relative to previous winters may have
been due to food resource loss resulting from salt spray that killed
leaves and possibly arthropods and fruit (Wunderle and Ewert 2018, p.
1). Because Kirtland's warblers readily shift sites on the wintering
grounds based on food availability, Kirtland's warblers would likely be
able to shift locations within and possibly between nearby islands as
an immediate post-hurricane response (Wunderle et al. 2007, p. 124).
Further, hurricanes likely produce new wintering habitat for Kirtland's
warblers by opening up closed canopy habitat of tall coppice and may
also help set back succession for existing suitable habitat (Wunderle
et al. 2007, p. 126). Coastal areas at most risk to storm surges (and
thus less suitable for development) may provide future habitat for
Kirtland's warblers (Wunderle and Ewert 2018, p. 1).
    In summary, uncertainties in modeling the projected effects of
climate change in The Bahamas, both spatially and temporally, create
some uncertainty in effects on the Kirtland's warbler's wintering
habitat and food availability. There is more confidence that
temperatures are likely to increase, and it is possible that there will
be a drying trend over much of the Caribbean. However, it is not clear
whether all islands will be equally affected by less precipitation. The
Kirtland's warbler population has increased dramatically during the
past drying trend (1979-2009) and recent drought (2013-2016) at its
wintering grounds. In addition, individual warblers have been reported
wintering outside of The Bahamas (see Distribution, above). Although
the extent of behavioral plasticity and adaptive capacity at the
species level to shift locations in response to the effects of climate
change in the Caribbean remains unknown, as a long-distance migrant,
the Kirtland's warbler is well suited, in terms of its movement
patterns and dispersal ability, to reach other locations both within
and outside of its current winter range where suitable winter habitat
and food resources may be more available under future temperature and
precipitation conditions.
Collision With Lighted and Human-Made Structures
    Collision with human-made structures (e.g., tall buildings,
communication towers, wind turbines, power lines, and heavily lighted
ships) kills or injures millions of migrating songbirds annually
(Bocetti 2011, pp. 177-178; reviewed in Drewitt and Langston 2008, p.
259; Longcore et al. 2008, pp. 486-489). Factors that influence the
likelihood of avian collisions with human-made structures include size,
location, use of lighting, and weather conditions during migratory
periods (reviewed in Drewitt and Langston 2008, p. 233). The presence
of artificial light at night and plate-glass windows are the most
important factors influencing avian collisions with existing human-made
structures (Ogden 1996, p. 4).
    There are five confirmed reports of Kirtland's warblers colliding
with human-made structures, all of which resulted in death. Two of
these deaths resulted from collisions with windows (Kleen 1976, p. 78;
Kramer 2009, pers. comm.), and three resulted from collisions with a
lighted structure, including a lighthouse (Merriam 1885, p. 376), an
electric light mast (Jones 1906, pp. 118-119), and a lighted monument
(Nolan 1954). Another report of a Kirtland's warbler that flew into a
window and appeared to survive after only being stunned by the
collision (Cordle 2005, p. 2) was not accepted as an official
documented observation of a Kirtland's warbler (Maryland Ornithological
Society 2010, unpaginated).
    Some bird species may be more vulnerable to collision with human-
made structures than others due to species-specific behaviors.
Particularly vulnerable species include: Night-migrating birds that are
prone to capture or disorientation by artificial lights because of the
way exposure to a light field can disrupt avian navigation systems;
species that habitually make swift flights through restricted openings
in dense vegetation; and species that are primarily active on or near
the ground (reviewed in Ogden 1996, p. 8; Gauthreaux and Belser 2006,
p. 67). Of the avian species recorded, the largest proportion of
species (41 percent) that suffer migration mortality at human-made
structures belong to the wood warbler subfamily (Parulinae), of which
many species exhibit the above-mentioned behaviors (Ogden 1996, p. 14).
    The Kirtland's warbler belongs to the Parulidae family, migrates at
night, typically occupies dense vegetation, and is often active on or
near the ground. Although Kirtland's warblers exhibit behavioral traits
that may contribute to vulnerability to collision with human-made
structures, little is known regarding how prone this species is to
collision. The majority of bird collisions go undetected because
corpses land in inconspicuous places or are quickly removed by
scavengers, postmortem (Klem 2009, p. 317). Additionally, while most
avian collisions take place during migration, detailed information
about Kirtland's warbler migration is still limited. The Kirtland's
warbler population is also small, reducing the probability of collision
observations by chance alone, compared to other species. These factors
have inhibited the gathering of information, and in turn, a more
comprehensive understanding of the hazards human-made structures pose
to the Kirtland's warbler. It is reasonable to presume, however, that
more Kirtland's warblers collide with human-made structures than are
    Solutions to reduce the hazards that cause avian collisions with
human-made structures are being implemented in many places.
Extinguishing internal lights of buildings at night, avoiding the use
of external floodlighting, and shielding the upward radiation of low-
level lighting such as street lamps are expected to reduce attraction
and trapping of birds within illuminated urban areas, and in turn,
reduce injury and mortality caused by collision, predation, starvation,
or exhaustion (reviewed in Ogden 1996, p. 31). The Service's Urban
Conservation Treaty for Migratory Birds program has worked with several
cities to adopt projects that benefit migrating birds flying through
urban areas between breeding and wintering grounds. For example, some
cities within the Kirtland's warbler's migration corridor, such as
Chicago, Indianapolis, Columbus, Detroit, and Milwaukee, have ``Lights
Out'' or similar programs, which encourage the owners and managers of
tall buildings to turn off or dim exterior decorative lights, as well
as interior lights, during spring and fall migration periods (National
Audubon Society 2019,
[[Page 54456]]
entire). These programs are estimated to reduce general bird mortality
by up to 83 percent (Field Museum 2007, p. 1).
    Additionally, migrating birds are not equally attracted to various
lighting patterns, and modifying certain types of lighting systems
could significantly reduce collision-related mortality. Removing
steady-burning, red L-810 lights and using only flashing, red L-864 or
white L-865 lights on communication towers and other similarly lit
aeronautical obstructions could reduce mortality rates by as much as 50
to 70 percent (Gehring et al. 2009, p. 509). On December 4, 2015, the
Federal Aviation Administration (FAA) revised its advisory circular
that prescribes tower lighting to eliminate the use of L-810 steady-
burning side lights on towers taller than 107 m (350 ft) (FAA Advisory
Circular 70/7460-1L), and on September 28, 2016, it released
specifications for flashing L-810 lights on towers 46-107 m (150-350
ft) tall. These lighting changes should significantly reduce the risk
of migratory bird collisions with communication towers.
    As noted previously concerning potential threats to migratory
habitat, if mortality during migration were limiting or likely to limit
the population to the degree that maintaining a healthy population may
be at risk, it should be apparent in the absence of the species from
highly suitable breeding habitat in the core breeding range. In fact,
we have seen just the opposite with increasing densities of breeding
individuals in core areas and a range expansion into what would appear
to be less suitable habitat elsewhere. This steady population growth
and range expansion occurred while the potential threats to the species
during migration were all increasing on the landscape (e.g., new
communication towers and wind turbines).
Synergistic Effects of Factors A Through E
    When threats occur together, one may exacerbate the effects of
another, causing effects not accounted for when threats are analyzed
individually. Many of the threats to the Kirtland's warbler and its
habitat discussed above under Factors A through E are interrelated and
could be synergistic, and thus may cumulatively impact Kirtland's
warbler beyond the extent of each individual threat. For example,
increases in temperature and evaporation could reduce the amount of
jack pine habitat available and increase the level of brood parasitism.
Historically, habitat loss and brood parasitism significantly impacted
the Kirtland's warbler and cumulatively acted to reduce its range and
abundance. Today, these threats have been ameliorated and adequately
minimized such that the species has exceeded the recovery goal. The
best available data show a positive population trend over several
decades and record high population levels. Continued habitat management
and brown-headed cowbird control at sufficient levels, as identified in
the Conservation Plan and at levels consistent with those to which
management agencies committed in the MOU and MOA, will assure continued
population numbers at or above the recovery criterion with the current
magnitude of other threats acting on the Kirtland's warbler.
Summary of Comments and Recommendations
    In the proposed rule published on April 12, 2018 (83 FR 15758), we
requested that all interested parties submit written comments on the
proposal by July 11, 2018. We also contacted appropriate Federal and
State agencies, scientific experts and organizations, and other
interested parties and invited them to comment on the proposal.
Newspaper notices inviting general public comment were published in The
Milwaukee Journal Sentinel on April 16, 2018, and in The Detroit Free
Press on April 23, 2018. We did not receive any requests for a public
hearing. The draft Post-delisting Monitoring Plan (PDM) was made
available on our website on June 7, 2018. During the comment period for
the proposed rule, we received a total of 42 comment letters or
statements directly addressing the proposed action. These included
comments from seven peer reviewers and 34 comments from the public
during the open comment period; all comments are posted on http://www.regulations.gov under Docket No. FWS-R3-ES-2018-0005. Many
commenters expressed their support or opposition to the proposed rule
without offering substantive information.
    In accordance with our peer review policy published on July 1, 1994
(59 FR 34270), we solicited expert opinion from 10 knowledgeable
individuals with scientific expertise that included familiarity with
Kirtland's warbler and its habitat, biological needs, and threats, as
well as familiarity with conservation biology, ornithology, climate
change, and population ecology. We received responses from seven peer
reviewers. Almost all of the peer reviewers supported the proposed
delisting rule, although one peer reviewer suggested that a more
cautious approach would be to downlist the species to provide a
``buffer'' of protection. Many peer reviewers commented that the
current status of Kirtland's warbler is accurately presented in the
proposed rule.
    We reviewed all comments we received from the peer reviewers and
the public for substantive issues and new information regarding the
delisting of Kirtland's warbler. Substantive comments we received
during the comment period are addressed below and, where appropriate,
are incorporated directly into this final rule. Comments that we
received on the PDM without reference to or comment on the proposed
rule are addressed separately in the PDM.
    Comment (1): Several peer reviewers and public commenters expressed
concern that additional funding will be needed to support the species
post-delisting. They discussed the need for sufficient funding to
ensure habitat management and brown-headed cowbird control will
continue at levels necessary to support the population above the
recovery goals. Several peer reviewers also mentioned that funding will
be necessary to support monitoring efforts to ensure any significant
changes to the species' population levels are detected. A reviewer also
stated that an income-producing fund has been created and appears to be
successful, but they were concerned over the uncertainty as to whether
it will be adequate to support conservation efforts post-delisting.
    Our Response (1): We acknowledge that the long-term survival of
Kirtland's warbler is dependent upon the continued implementation of
conservation programs that require agency commitment and sufficient
funding. The vast majority of conservation programs (with the exception
of brown-headed cowbird management) were previously funded through
agency appropriations and grants, and not funded through ESA recovery
funding. Thus, delisting Kirtland's warbler will not eliminate a major
source of funding that is tied to its listing status. In the 2016 MOU,
the MDNR, USFS, and Service reaffirmed their commitment to continue
managing and monitoring Kirtland's warblers if the species is delisted.
To supplement agency funding, which can fluctuate, the Kirtland's
Warbler Alliance has been working with partners to establish additional
funding sources for future conservation efforts. Recently, the American
Bird Conservancy (ABC) was awarded a grant to help establish a long-
term Kirtland's warbler endowment that would offset some of the
agencies' costs and support future Kirtland's warbler
[[Page 54457]]
conservation throughout the bird's full life cycle (Graff 2018,
    Previous funding of brown-headed cowbird management was provided
through ESA funding; therefore, a new funding source is needed to
secure brown-headed cowbird management efforts post-delisting. To
address this, the MDNR and Service developed a dedicated fund to be
used for brown-headed cowbird management and other high priority
conservation needs. At the time the proposed delisting rule was
published (83 FR 15758; April 12, 2018), the dedicated fund had greater
than $1 million. Since then, an additional $1.1 million was added,
increasing our certainty that sufficient funding for brown-headed
cowbird management will be available in the future. This account is
invested for long-term growth, and income generated will be used to
ensure sufficient brown-headed cowbird management to adequately reduce
brood parasitism of the Kirtland's warbler.
    Comment (2): Several peer reviewers discussed the issue of brown-
headed cowbird control. The majority expressed support of continuing
the brown-headed cowbird management program and asked for more detail
regarding how the agencies will monitor the rates of parasitism to know
when parasitism rates change, how the agencies will respond to
increases in parasitism rates, and whether sufficient funding exists to
continue to support the brown-headed cowbird program at historical
levels of trapping.
    Our Response (2): Brood parasitism has historically been one of the
primary threats to Kirtland's warbler, and thus the brown-headed
cowbird management program has been a critical component of the
recovery program. Recent research has shown a reduced brown-headed
cowbird population throughout the Kirtland's warbler's core range in
the northern Lower Peninsula. An experiment was initiated in 2015 to
evaluate the effect of a reduced trapping program on Kirtland's warbler
nest success. During a 3-year period (2015-2017), 3 of 385 Kirtland's
warbler nests were parasitized in areas with a spatially reduced
trapping program. Following these results, all trapping in the northern
Lower Peninsula was suspended for the 2018 nesting season. In 2018,
only one nest of over 140 was found to be parasitized. Additional
information and data have been added to this final rule to reflect the
most recent information on parasitism rates, including data from the
2018 nesting season.
    We fully expect brood parasitism rates to fluctuate and recognize
that permanent reductions to the brown-headed cowbird management
program are not prudent. Rather, an adaptive management approach is
appropriate to ensure adequate brown-headed cowbird management into the
future. We have included the need for continued research and monitoring
in the PDM to help inform future efforts.
    Based on the ongoing research, we do not expect that trapping
levels will need to return to previous levels for several years, and
may never return to historic levels. Through ongoing research, the KWCT
hopes to establish trigger points that would dictate when trapping
would be resumed and at what level. Through the MOA, and reaffirmed in
a letter dated November 9, 2017, the MDNR has agreed to assume
responsibility for the brown-headed cowbird management program. Funding
for the brown-headed cowbird management program will be available
through interest accrued from the brown-headed cowbird dedicated fund
(see our response to Comment (1)), or other agency funds through the
    External funding has been secured for the Smithsonian Migratory
Bird Center to continue monitoring brown-headed cowbird presence and
brood parasitism for the 2019 and 2020 nesting seasons. The results
from the cowbird monitoring research conducted during 2015-2020 will be
used to develop specific monitoring protocols that will be conducted in
accordance with the PDM. We also expect the KWCT to continue assessing
the need for further monitoring or research.
    Comment (3): Several peer reviewers discussed the importance of
continued habitat management for the Kirtland's warbler population. A
reviewer asserted that we made a major assumption in stating that
management agencies will continue to create habitat post-delisting.
Another comment discussed the uncertainty regarding timber
marketability and the importance of timber receipts in offsetting the
cost of Kirtland's warbler habitat management, and asked that this
topic be more explicitly addressed in the rule. Further, a reviewer
recommended a better plan on developing forestry techniques that
increase marketability of the timber, as well as finding creative ways
to fund future habitat management efforts. Many of the comments
received regarding continued habitat management related to ensuring
management would continue and how habitat management will be funded.
    Our Response (3): The management agencies have a long-standing
history of providing habitat for the Kirtland's warbler and have
described their commitment to continuing management for the Kirtland's
warbler in the Conservation Plan and the MOU. We recognize the
uncertainty over future timber markets and the impact that timber
receipts may have in offsetting the costs of habitat management. The
land managers and the KWCT have also recognized this uncertainty and
have started the process to develop and test alternative planting
techniques that would reduce costs and improve the marketability of
jack pine through increased growth rates while still providing
Kirtland's warbler nesting habitat. Currently, the Conservation Plan
indicates up to 25 percent of future habitat management, annually, may
incorporate non-traditional regeneration techniques designed to address
the marketability and regeneration of jack pine.
    Specific plans are not yet available, as the habitat management
planning process is dynamic. Alternative management techniques will
evolve over time and be adaptable to changing circumstances. A
subcommittee of the KWCT has routinely met over the last several years
to develop alternative techniques. Additional information regarding
timber marketability and future jack pine regeneration techniques has
been added to this rule.
    Habitat management will continue to be funded through appropriated
funds provided to the land management agencies for timber harvest and
reforestation. Additional funds may be available through the endowment
being developed by the Kirtland's Warbler Alliance and ABC, which is
described earlier in this rule.
    Comment (4): Several peer reviewers provided comments on the
Conservation Plan's allowance of up to 25 percent of habitat management
to be non-traditional habitat regeneration techniques. They stated that
the quality of Kirtland's warbler breeding habitat created through new
techniques is not known and could result in a loss of up to 25 percent
of breeding habitat and potentially a substantial decrease in the
abundance of Kirtland's warbler. The reviewers recommend any non-
traditional techniques be used as part of the annual habitat goals only
after they have been shown to be effective. They clarified that both
density of breeding pairs and fledgling production are important
metrics for evaluating the quality of non-traditional breeding habitat.
Another peer reviewer asked us to emphasize that the 25 percent
experimental habitat regeneration is a maximum and should not be
interpreted as an annual requirement. This reviewer also pointed out
that the 75 percent of
[[Page 54458]]
breeding habitat created using traditional methods is enough to support
the population above the recovery goal of 1,000 pairs and reflects the
best available science regarding breeding habitat use by the species.
    Our Response (4): We have clarified in this rule that the 25
percent experimental habitat amount is a maximum amount annually.
Managing habitat with traditional techniques at a minimum of 75 percent
of the annual objective will still provide enough breeding habitat to
maintain the species well above the recovery goal. Additionally, we
expect that the experimental habitat will still provide breeding
habitat for Kirtland's warbler but at potentially lower densities or
reduced nest success. These experimental designs will be closely
monitored to evaluate their effectiveness in regenerating jack pine and
providing Kirtland's warbler breeding habitat.
    Comment (5): Several peer reviewers also commented on the agencies'
commitment to continue conservation actions for Kirtland's warbler and
whether the level of commitment provided via the current MOA and MOU
are sufficient to support delisting. A peer reviewer expressed concern
regarding the level of commitment to continuing habitat management and
pointed out that the MOU indicates that management will occur ``only as
appropriated funds are available'' and that ``additional funds will be
necessary to meet these commitments.'' They also pointed out that the
MOU can be terminated at any time by any agency and asked whether the
agreements are legally binding. Multiple peer reviewers and several
public commenters indicated that the levels of commitment in the
existing MOU and MOA are sufficient to support delisting. One reviewer
asked if the MOU had expired and, if so, when it might be renewed.
Regarding conservation agreements on the wintering grounds, one
reviewer commented that they are not necessary prior to delisting,
given our understanding of threats to winter habitat.
    Our Response (5): The MOU is a synthesis of the land management
agencies' commitments to forest management, developed under the
requirements of Federal and State law that will remain in effect after
delisting, to sustain Kirtland's warbler. The MOU was first signed in
2011, was renewed in 2016, and currently expires in 2020. Prior and
subsequent to the MOU, habitat management and other conservation
programs were always dependent on annual appropriated funds provided to
the land management agencies. Further, MDNR did not have any legal
obligations under the ESA to conduct habitat management during the last
40 years while the species was listed, but MDNR adopted into their
forest plans the habitat management goals set forth by the Kirtland's
Warbler Recovery Team and later by the KWCT. The MOA is specific to
cowbird management and the development of a dedicated funding source
primarily for that activity, but possibly other activities in the
future if excess funding resources become available. The MOA was signed
in 2015 with no expiration date and stipulates that the Service and
MDNR will review progress under the MOA every 5 years to determine
whether any modifications are warranted. While not fully legally
binding, the MOU and MOA are built on a foundation of Federal and State
law guiding land management and further express the agencies'
commitments to continue managing for the species, regardless of the
species' status under the ESA.
    Comment (6): Several peer reviewers asked for additional detail
regarding the intensity and extent of population monitoring post-
delisting. A peer reviewer expressed concern over the lack of full
surveys (censuses) in recent years, noting that the last full
population survey was in 2015. Several reviewers questioned the recent
(2016) shift from full census to the less intensive survey effort and
requested that the MDNR sampling method be better explained. Several
peer reviewers indicated that MDNR should continue with the full census
until the proposed survey technique undergoes peer review and
publication in a reputable journal. One peer reviewer emphasized that
any reduced survey effort should be capable of providing a reliable
extrapolation of total breeding male abundance, so as to allow
comparison with past total singing/territorial male counts from
previous population censuses. Another reviewer commented that the
census techniques should be improved to assure accuracy, reduce
uncertainty, and improve ability to detect small population-level
changes. In addition, a reviewer noted that in areas where reduced
brown-headed cowbird trapping occurs (as compared to previous levels)
or experimental habitat management techniques are used, more intensive
population monitoring is necessary. Some reviewers also suggested that
the PDM should include monitoring of survival and reproductive success
in addition to the number of singing males. Furthermore, one peer
reviewer mentioned the possibility of using mist-netting as an
alternative to nest searching to estimate productivity.
    Our Response (6): We appreciate the comments regarding the need for
further details on how the Kirtland's warbler population will continue
to be monitored post-delisting. Our knowledge of the Kirtland's warbler
population and its response to habitat management has greatly been
informed by conducting an annual census using similar protocols over
several decades. We recognize that the complexity of conducting an
annual census has changed as the species has expanded from its core
breeding range. Further, the intensity of a monitoring effort should be
continually reevaluated in accordance with adaptive management needs
and the population size (e.g., for a smaller population, intensive
monitoring is more feasible and potentially more important). For a
recovered population, unless new information or concerns suggest
otherwise, a less-intensive monitoring effort (when compared to when
populations were critically imperiled) helps ensure staffing and
funding resources are used most effectively. Monitoring of the
Kirtland's warbler has routinely been coordinated by the respective
land management agencies in coordination with the Service and Recovery
Team, or more recently, the KWCT. As the species' population and range
has expanded, so has the time and resources needed to conduct a full
census. While the KWCT recognizes how critically important it is to
continue monitoring the species, it has also recognized that there may
be more efficient ways to monitor the species' status than a full
    In 2016, Michigan State University, in conjunction with MDNR,
developed a survey protocol designed to detect a 20 percent change in
the population. The recommended survey would randomly select 50 percent
of occupied stands on which the standard census protocol would be
conducted. By incorporating stand size and age with the observed number
of singing males, the survey would provide an estimate of the singing
male population with enough confidence to detect a 20 percent reduction
in individual singing males. The survey design was tested by using
previous census results from 2010, 2011, 2012, and 2013. In each case,
the reported census number fell within the survey protocols' 95%
confidence interval. Other land management agencies, including USFS and
WDNR, plan to continue periodic full censuses.
    We recognize that there may be instances where more precise
population monitoring is warranted.
[[Page 54459]]
When experimenting with alternative habitat regeneration techniques or
reduced brown-headed cowbird management levels, a higher level of
monitoring would need to be conducted in order to accurately determine
the warbler's response to those activities. The need for additional
monitoring will be determined by the management agencies, researchers,
and KWCT. This need is also addressed within the PDM.
    We believe that the monitoring proposed in the PDM is sufficient to
detect population-level trends, and MDNR's proposed sampling technique
will provide a sufficient estimate of the singing male population. The
KWCT will continue to evaluate monitoring protocols and may determine
that a periodic full census may be warranted as time and resources
    Comment (7): A peer reviewer asked for clarification on the
population level that will trigger intensified conservation efforts
necessary to ensure the population remains above the numerical recovery
goal of 1,000 pairs. Another emphasized that maintaining population
numbers above the recovery goal provides flexibility (and a buffer) if
new threats emerge.
    Our Response (7): In development of the Conservation Plan, the
agencies agreed that if the population drops below 1,300 singing males,
they would discuss the population decline, decide whether their
objectives and actions need to be changed, and implement these
recommended changes. The primary objective remains to keep the
Kirtland's warbler population above the numerical recovery goal of
1,000 pairs. However, any noted decline from current population levels
will be discussed amongst the agencies and the KWCT, and any
appropriate action will be taken.
    Comment (8): Several reviewers commented that a better
understanding of wintering habitat needs should be a high priority for
the KWCT and recommended fully mapping the extent of wintering habitat,
as well as further research on how various activities and land uses on
the wintering grounds impact the species.
    Our Response (8): Although threats to Kirtland's warblers on the
wintering grounds exist, the current extent and magnitude of these
threats are not significantly limiting Kirtland's warbler population
numbers, based on the species' continuous population growth over the
last two decades. If the population shows signs of decline in the
future, we will coordinate with the KWCT to assess all potential
stressors, including those occurring on the wintering grounds. The KWCT
and its Non-breeding Range Subcommittee recognize the importance of
continued research on the needs of the Kirtland's warbler on the
wintering grounds, specifically delineating wintering habitat and
assessing how land use may impact the species.
    Comment (9): Multiple peer reviewers commented on the species'
wintering distribution, and provided citations to incorporate into the
rule. One reviewer added that occasional vagrant Kirtland's warbler
sightings outside of the core islands should not give the impression
that suitable habitat is widespread elsewhere in the Caribbean; the
rule should be explicit about our ignorance regarding suitable habitat
elsewhere (outside of the core), as habitat suitability has not yet
been measured except for on Eleuthera Island.
    Our Response (9): The text under Distribution in this rule has been
updated to more clearly reflect this uncertainty regarding wintering
    Comment (10): Several comments received were related to our
analysis of the effects of climate change on the Kirtland's warbler's
breeding and wintering grounds. Two reviewers stated that the analysis
of climate change in the proposed rule was thorough and relied on the
best available science. One reviewer stated that delisting will not
prohibit the ongoing research to improve our understanding of future
potential threats. Another peer reviewer commented that current climate
change projections indicate that habitat suitability within the core
breeding range will remain suitable for supporting jack pine in this
century; another commenter stated that climate change could result in a
shift in the range toward Wisconsin. One reviewer mentioned that on the
wintering grounds, Kirtland's warbler could be negatively affected by
climate change, but added that there is much uncertainty and currently
a lack of strong evidence to suggest a major loss or degradation of
wintering grounds habitat will occur in the near future. Another
reviewer emphasized the importance of acquiring baseline data on
wintering habitat availability and quality to provide a context for
future climate change analysis. A reviewer commented that climate
change projections that predict an increased drought for the central
islands of The Bahamas may represent risk to the main wintering area
and recommended protecting drought-tolerant sites (e.g., freshwater
lens near the ground surface) where the Kirtland's warbler's preferred
fruit plants occur. Another reviewer provided the citation for a
recently published paper regarding future risks of heavy rainfall
events and extended periods of hurricane-force winds due to an
increasing trend for hurricanes to have decreased forward or
translational speeds (Kossin 2018, entire). Further, the reviewer asked
that the rule be updated to add observations of hurricane effects on
the island of San Salvador, where post-hurricane declines of Kirtland's
warblers have been observed.
    Our Response (10): Climate change predictions are variable and in
many cases uncertain. We reviewed the best available data using
multiple models and emission scenarios to evaluate the impact of
climate change on the Kirtland's warbler in the foreseeable future. On
the breeding grounds, temperature will very likely increase, and
precipitation will increase for parts of the year but may decrease at
the end of the growing season (Handler et al. 2014, pp. 72-75; Janowiak
et al. 2014, pp. 66-85). On the wintering grounds, temperatures will
also increase, which could result in rising sea level. The Caribbean is
experiencing a general drying trend, but there is temporal and spatial
    We will remain engaged with the KWCT and its Non-breeding Range
Subcommittee to monitor climate conditions and how they may impact the
Kirtland's warbler. We will also work with the KWCT as they engage The
Bahamas National Trust and other groups in an effort to identify and
protect critical sites in The Bahamas for Kirtland's warbler
    Additional discussion regarding the potential for climate change
has been added to this rule under Factor E: Climate Change.
    Comment (11): Almost all of the peer reviewers indicated their
support of delisting the Kirtland's warbler and stated that the
analysis in the proposed rule was sufficient to support delisting. Many
heralded the Kirtland's warbler as a success story of the ESA. One peer
reviewer, however, recommended we apply a more cautious approach and
instead reclassify (i.e., downlist) Kirtland's warbler as a threatened
species. Several public commenters had similar comments indicating that
the proposed delisting rule was premature, and we should maintain
protections to ensure we more fully understand proposed and recent
changes to habitat management and brown-headed cowbird control programs
before changing the status of the Kirtland's warbler.
    Our Response (11): During our analysis, we evaluated the status of
[[Page 54460]]
Kirtland's warbler to determine if the species met the definition of an
endangered or threatened species based on any of five factors: (A) The
present or threatened destruction, modification, or curtailment of its
habitat or range; (B) overutilization for commercial, recreational,
scientific, or educational purposes; (C) disease or predation; (D) the
inadequacy of existing regulatory mechanisms; or (E) other natural or
manmade factors affecting its continued existence. Based on the status
of the species and the known and foreseeable threats, we determined
that the species has recovered and does not meet the ESA's definition
of an endangered or a threatened species. Thus, the Kirtland's warbler
does not warrant listing under the ESA. While we appreciate the concern
and suggestion of a more cautious approach, delisting Kirtland's
warbler is warranted based on the best available information.
    Comment (12): One peer reviewer expressed concern over potential
forest pests causing a catastrophic loss of suitable habitat; the
reviewer acknowledges that the currently known insect or fungal threats
to jack pine or red pine are possible to manage, and forests in this
region are under the oversight of forest management agencies. The
reviewer added that the Kirtland's warbler may be less vulnerable to
catastrophic loss due to pests or disease outbreaks when compared to
historically lower population levels. One commenter expressed concern
over the effects of pesticides on the Kirtland's warbler and its insect
    Our Response (12): Our review of the best available science did not
identify any known threats to the status of the Kirtland's warbler from
forest pests, disease, or the use of pesticides. We acknowledge that
new threats from insects, fungi, other pests, or the use of a new
pesticide may emerge in the future, but our analysis concluded that the
species has good redundancy, representation, and resiliency, which
should allow the species to withstand potential future stressors.
    We agree with the reviewer that the management of forest pests and
disease primarily falls under the authority of the forest management
agencies. Through collaborative efforts, the KWCT and its Breeding
Range Subcommittee, the land management agencies' silviculturists, and
the forest product industry can collectively monitor these potential
threats and respond accordingly if the threats are determined to impact
Kirtland's warbler nesting habitat.
    We added additional discussion and references regarding forest
pests, disease, and pesticides to this rule (see discussions under
Factors A and E).
    Comment (13): A peer reviewer requested that additional discussion
be added regarding recreation, access, and development, including
current restrictions in areas occupied by the Kirtland's warbler, and
regarding changes that would occur if the Kirtland's warbler is
delisted. The reviewer expressed concern that unrestricted recreational
activity and nearby development could have unforeseen impacts on the
population and that this should be more explicitly considered in our
    Our Response (13): Currently, only a portion of the Kirtland's
warbler's nesting habitat in the northern Lower Peninsula is posted
closed during the species' breeding season by the respective land
management agency. Many of the recreational uses of the Kirtland's
warbler's nesting habitat (e.g., hunting, blueberry picking) are
typically conducted at times when impacts to the species are limited.
Further, in areas that are not posted closed, we have not seen evidence
of impacts to the species. Delisting Kirtland's warbler would not limit
the authority of the land management agencies to close areas as needed
to limit resource damage or protect sensitive species. We added
additional information and discussion related to other uses of the
Kirtland's warbler's nesting habitat to this rule (see Factor B
    Comment (14): Several peer reviewers provided additional
information and suggested additional references to support statements
in the proposed rule. This included information regarding mortality due
to lighted cruise ships in the Caribbean, presence of other avian brood
parasites (i.e., cuckoo species) in the Kirtland's warbler breeding
range, and new information on wintering habitat and distribution.
    Our Response (14): We appreciate the additional information
provided by the reviewers. We reviewed the additional information and
corresponding references, and we updated this final rule accordingly.
    Comment (15): A peer reviewer suggested adding a discussion of
reproductive rates to the ``Demographics'' section of the rule.
    Our Response (15): We added this discussion as suggested.
    Comment (16): A peer reviewer commented that the assumption
regarding number of singing males equating to number of breeding pairs
needs clarification and suggested caution when interpreting the number
of singing males as an indication of number of breeding pairs.
    Our Response (16): We added additional clarification to this rule
under Abundance and Population Trends.
    Comment (17): One commenter requested peer review and a public
comment period greater than or equal to 90 days.
    Our Response (17): The proposed rule was open for public comments
for 90 days, from April 12, 2018, through July 11, 2018, and we
solicited peer review on the proposal.
    Comment (18): One commenter asked for additional detail on State
regulatory protections if the Kirtland's warbler is delisted.
    Our Response (18): The Kirtland's warbler is currently protected by
State law in a number of States in the species' breeding and migratory
ranges under the respective State endangered species regulations.
Changing the Federal status of the Kirtland's warbler will not
automatically change the listing status of the Kirtland's warbler under
State law. Each State evaluates the current status of a species to
determine whether it warrants protection under the State's respective
statutes. We expect that each State will evaluate the State listing
status of the Kirtland's warbler at some point in the next several
years, but we cannot speculate as to their decisions under State law.
Similarly, the Kirtland's warbler is also protected as endangered under
Canada's Species at Risk Act of 2003. Canadian officials will decide
whether to retain protected status for the Kirtland's warbler based on
their laws and regulations.
    Comment (19): One commenter asked if we were proposing delisting to
benefit the wind industry and suggested the proposed rule was motivated
by reducing regulatory burden to make it easier to get ``wind towers in
place in rural Ohio.''
    Our Response (19): Our determination is based solely on the status
of the species utilizing the best available science, and our status
review was initiated due to the species' population and range expansion
in recent years, the development of the Kirtland's Warbler Conservation
Plan and MOU, and development of a long-term endowment and MOA to
conduct brown-headed cowbird management.
    Section 4 of the ESA (16 U.S.C. 1533), and its implementing
regulations at 50 CFR part 424, set forth the procedures for
determining whether a species is an endangered species or threatened
species and should be included on the Federal Lists of Endangered and
Threatened Wildlife and Plants. The
[[Page 54461]]
ESA defines an endangered species as any species that is ``in danger of
extinction throughout all or a significant portion of its range'' and a
threatened species as any species that is ``likely to become an
endangered species within the foreseeable future throughout all or a
significant portion of its range.''
    Under section 4(a)(1) of the ESA, we determine whether a species is
an endangered species or threatened species because of any of the
following factors: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence. These same factors apply whether we
are analyzing the species' status throughout all of its range or
throughout a significant portion of its range.
Determination of Status Throughout All of the Kirtland's Warbler's
    We have carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
to the Kirtland's warbler. We assessed the five factors to evaluate
whether the species is in danger of extinction, or likely to become so
in the foreseeable future, throughout all of its range. The size of the
Kirtland's warbler population is currently at its known historical
maximum, which is nearly 10 times larger than it was at the time of
listing and more than double the recovery goal. The population's
breeding range also expanded outside of the northern Lower Peninsula to
areas in Michigan's Upper Peninsula, Wisconsin, and Ontario. This
recovery is attributable to successful interagency cooperation in the
management of habitat and brood parasitism. The amount of suitable
habitat has increased by approximately 150 percent since listing,
primarily due to the increased amount of planted habitat generated from
adaptive silvicultural techniques. Brown-headed cowbird control has
been conducted on an annual basis within the majority of Kirtland's
warbler nesting areas since 1972, and has greatly reduced the impacts
of brood parasitism.
    During our analysis, we found that impacts believed to be threats
at the time of listing have been eliminated or reduced, or are being
adequately managed since listing, and we do not expect any of these
conditions to substantially change after delisting and into the
foreseeable future. Population modeling that assessed the long-term
population viability of Kirtland's warbler populations showed stable
populations over a 50-year simulation period with current habitat
management and maintaining sufficient brown-headed cowbird removal (see
Population Viability, above). Brood parasitism and availability of
sufficient suitable breeding habitat are adequately managed through the
Kirtland's Warbler Breeding Range Conservation Plan and the 2016 MOU.
The Conservation Plan and the MOU acknowledge the conservation-reliant
nature of the Kirtland's warbler and the need for continued habitat
management and brown-headed cowbird control, and affirm that the
necessary long-term management actions will continue. The species is
resilient to threats including changing weather patterns and sea level
rise due to the effects of climate change, collision with lighted and
human-made structures, impacts to wintering and migratory habitat, and
cumulative effects, and existing information indicates that this
resilience will not change in the foreseeable future. These conclusions
are supported by the available information regarding the species'
abundance, distribution, and trends. Thus, after assessing the best
available information, we conclude that the Kirtland's warbler is not
in danger of extinction throughout all of its range, nor is it likely
to become so within the foreseeable future.
Determination of Status Throughout a Significant Portion of the
Kirtland's Warbler's Range
    Under the ESA and our implementing regulations, a species may
warrant listing if it is in danger of extinction or likely to become so
in the foreseeable future throughout all or a significant portion of
its range (SPR). Where the best available information allows the
Service to determine a status for the species rangewide, that
determination should be given conclusive weight because a rangewide
determination of status more accurately reflects the species' degree of
imperilment and better promotes the purposes of the ESA. Under this
reading, we should first consider whether the species warrants listing
``throughout all'' of its range and proceed to conduct a ``significant
portion of its range'' analysis if, and only if, a species does not
qualify for listing as either an endangered or a threatened species
according to the ``throughout all'' language.
    Having determined that the Kirtland's warbler is not in danger of
extinction or likely to become so in the foreseeable future throughout
all of its range, we now consider whether it may be in danger of
extinction or likely to become so in the foreseeable future in an SPR.
The range of a species can theoretically be divided into portions in an
infinite number of ways, so we first screen the potential portions of
the species' range to determine if there are any portions that warrant
further consideration. To do the ``screening'' analysis, we ask whether
there are portions of the species' range for which there is substantial
information indicating that: (1) The portion may be significant; and
(2) the species may be, in that portion, either in danger of extinction
or likely to become so in the foreseeable future. For a particular
portion, if we cannot answer both questions in the affirmative, then
that portion does not warrant further consideration and the species
does not warrant listing because of its status in that portion of its
range. We emphasize that answering these questions in the affirmative
is not a determination that the species is in danger of extinction or
likely to become so in the foreseeable future throughout a significant
portion of its range--rather, it is a step in determining whether a
more detailed analysis of the issue is required.
    If we answer these questions in the affirmative, we then conduct a
more thorough analysis to determine whether the portion does indeed
meet both of the SPR prongs: (1) The portion is significant; and (2)
the species is, in that portion, either in danger of extinction or
likely to become so in the foreseeable future. Confirmation that a
portion does indeed meet one of these prongs does not create a
presumption, prejudgment, or other determination as to whether the
species is an endangered species or threatened species. Rather, we must
then undertake a more detailed analysis of the other prong to make that
determination. Only if the portion does indeed meet both SPR prongs
would the species warrant listing because of its status in a
significant portion of its range.
    At both stages in this process--the stage of screening potential
portions to identify any portions that warrant further consideration
and the stage of undertaking the more detailed analysis of any portions
that do warrant further consideration--it might be more efficient for
us to address the ``significance'' question or the ``status'' question
first. Our selection of which question to address first for a
particular portion depends on the biology of the species, its range,
and the threats it faces. Regardless of which question we address
first, if we reach a negative answer with respect to the first question
[[Page 54462]]
that we address, we do not need to evaluate the second question for
that portion of the species' range.
    For the Kirtland's warbler, we chose to evaluate the status
question (i.e., identifying portions where the Kirtland's warbler may
be in danger of extinction or likely to become so in the foreseeable
future) first. To conduct this screening, we considered whether the
threats are geographically concentrated in any portion of the species'
range at a biologically meaningful scale.
    Kirtland's warblers occupy different geographic areas (breeding
grounds, migratory routes, wintering grounds) throughout the course of
a year. Although there are different threats acting on the species on
the breeding grounds, migratory routes, and wintering grounds (see
discussion under Factors A through E, above), the threats associated
with these areas are uniformly spread across each area (e.g., threats
on the breeding grounds are uniform across the breeding range, threats
on the wintering grounds are uniform across the winter range). The
entire population moves through the full annual cycle (breeding,
migration, and wintering) and functions as a single panmictic
population (see discussion under ``Genetics,'' above); therefore, these
different geographic areas do not represent biologically separate
populations that could be exposed to different threats.
    We examined the following threats: Availability and distribution of
breeding, migration, and wintering habitat; pesticides; brood
parasitism; the effects of climate change; collision with lighted and
human-made structures; and the cumulative effects of these threats. We
found no concentration of threats in any portion of the Kirtland's
warbler's range at a biologically meaningful scale. If both (1) a
species is not in danger of extinction or likely to become so in the
foreseeable future throughout all of its range and (2) the threats to
the species are essentially uniform throughout its range, then the
species could not be in danger of extinction or likely to become so in
the foreseeable future in any biologically meaningful portion of its
range. For the Kirtland's warbler, we found both: The species is not in
danger of extinction or likely to become so in the foreseeable future
throughout all of its range, and there is no geographical concentration
of threats so the threats to the species are essentially uniform
throughout its range. Therefore, no portions warrant further
consideration through a more detailed analysis, and the species is not
in danger of extinction or likely to become so in the foreseeable
future in any significant portion of its range. Our approach to
analyzing SPR in this determination is consistent with the court's
holding in Desert Survivors v. Department of the Interior, No. 16-cv-
01165-JCS, 2018 WL 4053447 (N.D. Cal. Aug. 24, 2018).
    Our review of the best available scientific and commercial
information indicates that the Kirtland's warbler is not in danger of
extinction or likely to become an endangered species within the
foreseeable future throughout all or a significant portion of its
range. Therefore, we find that listing the Kirtland's warbler as an
endangered species or a threatened species under the ESA is not
warranted at this time.
    We have carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
to the Kirtland's warbler. The threats that led to the species being
listed under the ESA (i.e., primarily loss of the species' habitat
(Factor A) and effects of brood parasitism by brown-headed cowbirds
(Factor E)) have been removed, have been ameliorated, or have been
appropriately managed by the actions of multiple conservation partners
over the past 50 years. These actions include habitat management,
brown-headed cowbird control, monitoring, research, and education.
Given commitments shown by the cooperating agencies entering into the
Kirtland's warbler MOU and the long record of engagement and proactive
conservation actions implemented by the cooperating agencies over a 50-
year period, we expect conservation efforts will continue to support a
healthy, viable population of the Kirtland's warbler post-delisting and
into the foreseeable future. Furthermore, there is no information to
conclude that, at any time over the next 50-year window (as we define
the foreseeable future for this species), the species will be in danger
of extinction. Thus, we have determined that none of the existing or
potential threats, either alone or in combination with others, is
likely to cause the Kirtland's warbler to be in danger of extinction
throughout all or a significant portion of its range, nor are any of
the existing or potential threats likely to cause the species to become
endangered within the foreseeable future throughout all or a
significant portion of its range. On the basis of our evaluation, we
conclude that, due to recovery, the Kirtland's warbler is not an
endangered or threatened species. We, therefore, remove the Kirtland's
warbler from the Federal List of Endangered and Threatened Wildlife at
50 CFR 17.11(h) due to recovery.
Effects of This Rule
    This rule revises 50 CFR 17.11(h) by removing the Kirtland's
warbler from the Federal List of Endangered and Threatened Wildlife. On
the effective date of this rule (see DATES, above), the prohibitions
and conservation measures provided by the ESA, particularly through
sections 7 and 9, no longer apply to this species. Federal agencies are
no longer required to consult with the Service under section 7 of the
ESA in the event that activities they authorize, fund, or carry out may
affect the Kirtland's warbler. There is no critical habitat designated
for this species; therefore, this rule does not affect 50 CFR 17.95.
Removal of the Kirtland's warbler from the List of Endangered and
Threatened Wildlife does not affect the protection given to all
migratory bird species under the MBTA.
Post-Delisting Monitoring
    Section 4(g)(1) of the ESA requires us, in cooperation with the
States, to implement a system to monitor for not less than 5 years the
status of all species that have been recovered and delisted. The
purpose of this requirement is to develop a program that detects the
failure of any delisted species to sustain itself without the
protective measures provided by the ESA. If, at any time during the
monitoring period, data indicate that protective status under the ESA
should be reinstated, we can initiate listing procedures, including, if
appropriate, emergency listing.
    The PDM for the Kirtland's warbler was developed in coordination
with our Federal, State, and other partners. The PDM is based upon
current research and effective management practices that have improved
the status of the species since listing. Ensuring continued
implementation of proven management strategies, such as brown-headed
cowbird control and habitat management, that have been developed to
sustain the species is a fundamental goal of the PDM. The PDM
identifies measurable management thresholds and responses for detecting
and reacting to significant changes in the Kirtland's warbler's
numbers, distribution, and persistence. If declines are detected
equaling or exceeding these thresholds, the Service, in combination
with other PDM participants, will investigate causes of these declines.
The investigation will be to determine if the Kirtland's warbler
warrants expanded monitoring, additional research, additional habitat
protection or brood
[[Page 54463]]
parasite management, or resumption of Federal protection under the ESA.
For example, monitoring Kirtland's warbler singing males, annual
habitat management acres, and brown-headed cowbird abundance or
parasitism rates will inform partners on the Kirtland's warbler's
status. If the population falls below 1,300 pairs, this would trigger
the partners to (1) schedule a meeting, (2) discuss what is causing the
decline, (3) decide how to respond, and (4) implement the recommended
changes. The PDM requires census or selectively sampling the Kirtland's
warbler breeding population every other year for a period of 12 years.
The final PDM plan is available at https://www.fws.gov/midwest/Endangered/birds/Kirtland.
Required Determinations
National Environmental Policy Act
    We determined that we do not need to prepare an environmental
assessment or an environmental impact statement, as defined under the
authority of the National Environmental Policy Act of 1969 (42 U.S.C.
4321 et seq.), in connection with regulations adopted pursuant to
section 4(a) of the ESA. We published a notice outlining our reasons
for this determination in the Federal Register on October 25, 1983 (48
FR 49244).
Government-to-Government Relationship With Tribes
    In accordance with the President's memorandum of April 29, 1994,
``Government-to-Government Relations with Native American Tribal
Governments'' (59 FR 22951), Executive Order 13175, Secretarial Order
3206, the Department of the Interior's manual at 512 DM 2, and the
Native American Policy of the Service, January 20, 2016, we readily
acknowledge our responsibility to communicate meaningfully with
recognized Federal Tribes on a government-to-government basis. We
contacted the tribes in the Midwest within the range of the Kirtland's
warbler and requested their input and comments on the proposed
delisting rule.
References Cited
    A complete list of all references cited in this rule is available
at http://www.regulations.gov under Docket No. FWS-R3-ES-2018-0005 or
upon request from the Field Supervisor, Michigan Ecological Services
    The primary authors of this rule are staff members of the Michigan
Ecological Services Field Office in East Lansing, Michigan, in
coordination with the Midwest Regional Office in Bloomington,
List of Subjects in 50 CFR Part 17
    Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, Transportation.
Regulation Promulgation
    Accordingly, we amend part 17, subchapter B of chapter I, title 50
of the Code of Federal Regulations, as set forth below:
1. The authority citation for part 17 continues to read as follows:
    Authority: 16 U.S.C. 1361-1407; 1531-1544; 4201-4245, unless
otherwise noted.
Sec.  [thinsp]17.11  [Amended]
2. Amend Sec.  [thinsp]17.11 in the table in paragraph (h) by removing
the entry for ``Warbler (wood), Kirtland's'' under ``BIRDS'' from the
List of Endangered and Threatened Wildlife.
    Dated: August 29 2019.
Stephen Guertin,
Principal Deputy Director, U.S. Fish and Wildlife Service, Exercising
the Authority of the Director, U.S. Fish and Wildlife Service.
[FR Doc. 2019-22096 Filed 10-8-19; 8:45 am]